Hi Paul ,
I can understand your frustration from practicing as myself but often times I would take a refresh by either doing something else remember Khan Academy is a tool to help utilize with your studies this can be combined with other learning approaches.

If you have any questions on how to use Khan Academy I will be happy to help you.

Remember we learn things with time sometimes we need to take a much needed break from our work to understand homework subjects at least this technique works for me.

As I am on the same journey as you with learning and being a Student I will be happy to help you and answer any questions you have never be afraid to ask for help.
Proud to be a Khan Academer
Katrina

Don't be afraid to use the "hint" option and/or watch the associated video to help you understand the topic better when you get frustrated. It's easier to get 3, 5, or however many your coach assigned right in a row if you totally understand the topic. I find that working the problems out on paper helps tremendously as well.