How to code exercises like the ones i can find in the math courses?

I've taken most of the KA programming courses and i wish to start and code some exercises to help me review "old" stuff. It's something i wish to do for myself not only for review purposes, but also to practice my newly acquired skills. Of course if i manage to produce something good enough i will gladly share it with the community.

Any suggestion is very welcome :)

Keep learning and stay awesome.