On the other hand, I failed my maths exam. There were various reasons for this, but one was simply that I spend to long looking at textbook, and not enough time answering questions. A full quarter of the questions in the exam were totally new to me; I had absolutely no idea how to even begin answering them.
The moral of the story? I would pay good money for a website that provided a set of questions that covered everything I needed to know. Obviously that's a big ask, especially at the university level. Perhaps you could allow users to define what categories of questions they need to be able to handle, or even create rules for generating new sets of questions. If I could spend 2 hours defining what questions I should be asked (and then share those settings with others in my class), then spend the rest of the day practicing those questions, that would be a day well spent.
What would I pay for that? Easily $20/semester, probably closer to $50.
Another way I could use this website is for revision or passive learning. Start with basic maths, and slowly add new categories of questions (negative numbers, then algebra, then calculus). If you could somehow generate how to solve the question, that would be even better - you could have an "I'm stuck, how do I solve this" button that would be perfect for learning at your own pace. Alternatively, you could just have one 'methods' page per category of questions, and every question of that type would link to that page. It would be feasible to hand-write those pages, or allow others to write them (or even just add their own notes that only they see).
Also, you might want to learn about spaced repetition learning - perhaps it's something you could implement.
If you don't want to use all (or any) of these ideas, that's fine. What you've got is great, but I hope my ideas get you thinking!
And finally, best of luck. I hope you change (this corner of) the world.