Hi RB,

A mastery challenge should be available to level up. If the mastery challenge has not appeared for over a week then it's a technical issue. You can file a Service Request  and the Khan Academy Support team can get back to you with the technical issues your having.

I am experiencig the same issue with this Systems of Linear equations word problems: Level 2 skill. I have practiced it few days ago but Khan Academy's World of Math never offers me to proceed to level 1, 2 and master this skill, as it does with all the other skills. It seem to me, that since I have practiced the skill, KA always wants to offer me new mastery challenge (so I don't see the "practice new skill first" of "another skill will be available in 7 hours" now), but then it always offer me another skill that I've already mastered instead of the "Systems of Linear equations word problems: Level 2" one.

I have already contacted the support team but I got just response about how the system of completing the skills works (which I know quite well myself, since I have completed more than 1,100 skills in my world of math mission yet... :) ). 

@Martin I filed the service request (as suggested by Katrina). I am told team is aware of the issue and it's on their TODO list. Sorry I don't have anything that would actually help. 

Hi RB,
Thank-you for filling a Service request this is a good response from the team it means that a high number of users are having the same issues and that it's priority with the information you provided like browsers, systems etc.you help tech staff find the bugs unfortunately with coding this could take time so I or the team can't guarantee when it will be fixed but it does mean that this issue is known.
If I get any updates myself or technical work a rounds I will let you know. Thank-you again for your help the team appreciates​ the time you have put in to report this technical issue . Also if you ever have any other questions etc. I will be happy to help you both.

I have the same issue with “Systems of linear equations word problems.”

I have only this skill left to master. I leveled it up to Level 2 through the Practice system, but the World of Math Mastery Challenge never offers it. It put me through countless exercises from the kindergarten to AP Calculus BC, but not that one.

99%! My best friend promised me chocolate if I can complete the World of Math series. Understand my frustration! :)

I am having exactly the same problem with this skill.

"Systems of linear equations word problems: Level 2" never appears in any mastery challenges on the World of Math page, so it remains unmastered no matter how many times I attempt a mastery challenge.

I believe this skill used to be part of the Class 7 (India) mission, but it no longer appears there, which might explain why it seems to be in a kind of limbo...

I will be extremely grateful to anyone who can fix this.

I ran into this problem today too, and have already submitted a problem report for it.

I'm also seeing a difference between the completion statistics on the mission page for the World of Math and the completion statistics for the World of Math on the progress tab on my profile page.

The profile page shows 1 mastered skill fewer than the mission page, and 2 skills not started that don't even show at all on the mission page.

I am in the same way.Does anyone know how to solve this problem?The KA team seems to have another "important" stuff to do ...

I have the same problem. Does anyone has found a workaround to this problem?

Solution (at least it worked for me): Change the language to:(And try some Mastery challenges)

If this language does not work for you ...try another language.Obs: the exercises are in English.

ΜΑΓΝΥΣ 's solution worked for me too. Thank you very much ΜΑΓΝΥΣ .

Me too. More than 5 months and still not fixed? Since this skill is the very last skill in the grid, I would guess that it's a simple "off by one" error when selecting tasks for Mastery Challenges (for example, choosing skills that are "<" the max skill rather than "<=", or using a Python "range(max_skill)" statement that gives numbers from 0 to max_skill-1 instead of to max_skill).

I would be happy to debug this code if someone would let me see it.

I tried emailing about this months ago and the responses I received were very unhelpful, but ΜΑΓΝΥΣ's solution worked perfectly.

I'm surprised at how long they are taking to fix this, and that they never shared this workaround with me.

Having this problem as well, apparently 8 months was not enough to debug this code and ΜΑΓΝΥΣ's solution didnt worked for me =/ try multiple languages all of them shows "No mastery challenges available. Practice something new!", the only difference is that it shows it in other languages

ΜΑΓΝΥΣ 's solution worked for me too. Thank you very much ΜΑΓΝΥΣ !

hmmm.. same problem, solution doesn't work for me yet, I'll try again tomorrow. btw: some exercises stay in English but others don't.

EDIT: Today the solution worked, maybe I didn't wait long enough for the mastery challenge to appear yesterday. Still, and the reason is pictured above, getting this thing fixed will definitely make people happy.

I'm experiencing this same bug myself, why hasn't this been fixed already?

Come on guys, I understand that you have other things on your list to do, but there is really no excuse for this. If the dev team can't fix the skill after over a full year, then they should either remove it or just recreate it completely, all the new skills that were added recently work just fine, so I don't see what's so impossible about fixing this one?

 And I also understand that Khan Academy is a nonprofit organization, but as far as I can tell it receives literally millions of dollars in donations every single year to work with, and yet you still don't have the time or manpower to fix probably one of, if not the most popular section on the entire site?

 This seems like something that would only require someone to take a few minutes of their time to look into, are we really supposed to believe that there hasn't been a single opportunity in over an entire year? Don't take that the wrong way, I actually really love this site, and I want to support it so it can become even more mainstream and widely available than it already is, I think that it's a great concept and works very well for learning, that's the reason why I've put so much time into it.

  But if you don't work with your more devoted and serious users, and communicate with them, then how can you expect any loyalty? The people posting on this thread are the ones who have spent probably hundreds of hours on this site just to get anywhere near 99% on this mission, can you really not spare a few minutes for them? What kind of support is it to send in a ticket for a problem, and be told that it's been a known issue for over a year, and they just don't feel like fixing it?

 You need to stop adding new content and changing the visual design of the site, when you know already that some of your most popular features are still broken. Fix what isn't working right before you add anything new.

Sorry about the rant, I just didn't feel like waiting another three years or so for this to finally be looked into.

@Scourge,

KA has been working on a NEW mastery system, which is probably why this hasn't been fixed yet. Read more about it here!

- https://khanacademy.zendesk.com/hc/en-us/community/posts/360018942511-Update-New-Mastery-System

- https://khanacademy.zendesk.com/hc/en-us/articles/115002552631-What-are-Course-and-Unit-Mastery-

To Jett Burns - as long as the Missions are still part of Khan Academy, there are going to be people attempting them. If they’re no longer the preferred form of mastery by those who run Khan Academy, they should be turned off. Okay, maybe they are here for the benefit of those who have started them.

Because of the presence of this topic, and of course its underlying cause, I was referred to here yesterday when I had a different but similar problem (reported via Report a Problem) in a subject that doesn’t have a Mission. I was told to follow Magnus’ method that included changing my language. I felt this was a “knee jerk” reaction to my problem report, especially since I had this issue in a subject that doesn’t even have a Mission, plus I don’t know where I’m supposed to change my language (in my profile on the web site? in the app? in my iPad’s settings, systemwide for all apps?) and how to do it once I’m there.

So, Khan Academy should keep the Missions working properly. Plus, I think the new mastery system sucks, and you know how much I dislike them? Because I have never, ever before used the word “sucks” in this cotext before!

I'm somewhat peeved that the excuse I was given was the exact same kind I complained about in my post. I don't know if I can speak for the other users here, but I consider most of the recent changes to the site to be purely cosmetic; And I'm not really sure how this newest one is any different. What is the point of changing the way progress is displayed... when you can't completely progress to begin with? I don't even really care how the content looks, I only want to be able to finish the mission after all this time.

P.S: I already tried the language trick with all of them, and on multiple devices. It doesn't seem to make any difference

To Scourge and the others - I have World of Math on the backburner, but I may attempt to complete it, so I am interested in seeing it resolved. (Right now, it’s not in the iPad app where I do most of my Khan Academy work, so I’d have to take time to finish anything not covered in another course on the web site.)

Personally, I have wondered if this was due to a rounding issue, that even people who are seeing 100% got some level of completion that worked out to actually being 99.5 or higher, while those who are seeing 99% got 99.499999 (or however many decimal places they use) or lower.

Hey Regina - As far as I can tell it's just this one skill. I was already at 99% completion with only the one remaining long before they added about 70 new skills to the world of math mission, which bumped my overall completion back down to 95%. Yet despite the change in percentage, I still find that I can't master that particular skill, even though the newer ones all work fine.

I think that this one skill is always broken for everyone at any level of completion, it's just that no one really notices until they're near 100% completion, because it's a miscellaneous skill like the one you mentioned, you can't access it from anywhere but the world of math mission itself, so most people never even find out that it exists until the very end.

To Regina’s reply to me, it wouldn’t surprise me if missions were removed entirely soon, since this new “Unit Mastery” provides a mastery system for many more subjects on KA other than Math. It doesn’t make sense for them to spend so much time developing it if it didn’t become the primary mastery system. If you are following KA on social media you would know that KA has announced “new mastery learning features”; missions seem to be fading away.

I will personally investigate the technical aspect of this particular math skill and see what happens when I try to master it. Once I have more info I’ll likely create my own ticket about this and ask for a developer to respond to this post.

Can you please post screenshots of your World of Math mission page? I found the skill and can practice it, but it’d be great to see what you are seeing. Here’s how to take a screenshot:
https://khanacademy.zendesk.com/hc/en-us/articles/203411500-How-do-I-take-a-screenshot-

it still allows me to start the challenge, but it always just chooses one or two skills I've already mastered

Jett, if Khan Academy ever does get rid of missions, I hope they will announce it at least a month ahead of time so that those of us who are working on missions can have enough time to finish them. I had at one point finished all of the courses with missions (yes, even Kindergarten math) except for World of Math. Now, several of the ones I’ve finished, especially the calculus ones, have new skills added. I want to do these new skills and get back to 100%, but I’m working on Statistics and probability and don’t want to lose momentum on this one right now. However, if Khan Academy were to suddenly announce that the missions would be going away on, say, October 15, I would probably turn my attention to them almost immediately. Now, if they mentioned a date in the future, such as January 1, 2019, then I would probably finish up Statistics and probability first.

Scourge, I have some ideas for you, but I want to be in the Chrome browser on my Windows 10 laptop and make some screen prints to upload here first. I will not have time to do this today (Tuesday, Sept. 11/11 Sept. 2018) but will try to find time to do this later this week.

To Scourge and anyone else, here is how I think you can get this skill leveled up to Mastered.

1. Go to the World of Math page, which is at https://www.khanacademy.org/math/ (not easy to find, and I have bookmarked/favorited it so I can get there), and then choose the Mission tab.

2. Under the circle that shows your progress and the totals for each level, look for and then click on "Show all skills". (This is shown this way in your screen print. Others may already see their skills with the notation "Hide skill breakdown". If this is the case for you, keep it this way.)

3. You should now see a grid of color-coded squares. The one you in which you are most interested is the one that's the Practiced color, very light blue. In the below image from my computer, it is in the second row of the grid.

Hover your mouse over that square until you see a description of the skill:

4. Now actually click on that square. This will add it to the list of skills for you to practice when you go into the Mastery Challenge. It will be marked, "YOU ADDED". If you clicked on the wrong one, look for "Remove" just below the description.

To be honest, I have not tried this myself and am not yet ready to turn my focus away from my current Khan Academy studies to see if it works. But if you decide to try it, please let us know if it works for you. Something tells me I may need to do this eventually, too.

Here's something else to try. If you can figure out which course and unit the skill you show as only "practiced" is contained, go to the page for this unit. As a result of some differences between the Mission mastery system and the new one, some exercises that were previously practiced need to be done again even if you eventually got 100% on them. (Usually, this occurs for us 100%-obsessors if we get a fairly low score the first time through but eventually get 100%.) Chances are, you'll find this supposedly-practiced exercise shows "Try again". If this is the case for you, do the practice here until you get at least the minimum number correct (5 of 7 in this example, or 100% if that's your way of doing things).

If you don't know where this practice exercise is, Google "Khan Academy", "practice", and the practice exercise's name. This may actually take you to the exercise itself, where you can level up. Or you may be able to figure out the location by the URL shown in Google under the page name.

ΜΑΓΝΥΣ's solution worked for me in the past, but after they added the new exercises I have a new problem.

I'm back at 99%, and now the exercises stuck at level one are Interpreting negative numbers (temperature and elevation) and Estimate center using histograms. Changing the language doesn't help get these two exercises to appear in the mastery challenge.