Hi there!

Thank you for sharing your suggestion for us to add the mastery feature to the differential equations section. I've passed this feedback along to the appropriate team so they can review not only this section but any other courses that might need a boost.

As we grow and expand, we’re continuing to add new content to offer a better education at Khan Academy. Investing more heavily in the content team is actually one of our major initiatives.

Thank you for being part of our community!

Warm regards,

Alex