Hi William,

There is a known bug that causes one of the skills to not appear in the mastery challenges. Unfortunately, there is not a fix or workaround available for the bug at this time.

Additionally, it is also worth noting that the World of Math mission will be removed in June 2020 along with the rest of the Mission system, so I don't expect a fix to be released for this issue. You can learn more about the Mission removal here.

Sorry I couldn't be of more help! Please let me know if you have any additional questions!

Devestating news. I was rushing to reach this goal before the missions get junked! Oh well. Thanks for the reply

Plus, we have complained about this for 4+ years.

So it definitely will not get fixed.

Just delete the bogus skill.  KA deletes skills all the time. 

And why was this skill added just before the take down of the Missions?  I was at 100% mastered before I happened to check the missions again before they were to be deleted to see if anything changed.  And, lo and behold, I discovered two new skills.  One could be mastered and this last one cannot! I'm curious if we are all seeing the same skill there.  I'm seeing "Use ratios in right triangles."  I've gone through the list of skills in WoM and can't find this.  It's almost like it's a data entry error.  It reminds me of the time there were some skills in Portuguese right at that same location in the matrix that would never show up in the mastery.  KA eventually manipulated some data to "solve" that issue.

I guess the legacy of "Missions" is that at the end no one on earth will have 100% mastery.  It seems quite cruel that KA would announce the end of missions and then move the goal posts just before the end and dash the hopes of thousands.  Very sad.

Update: Good news!!  On a lark I tried the missions one last time and after doing the skill I had exited on earlier, the missing skill finally popped in.  I guess they fixed the problem -- Thanks Evan!

Try it today, but make sure you triple check your work!

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