While I never went as far as QM I learned a lot of math by listening to a teacher walk though the problem. I have had plenty of classes where I could not read the teachers handing writing and I still got A's on the final.

PS: As a rule I never studied which was fine to get the equivalent of a major in CS, and a minor in math. (I was like 3 classes from a double major, but I took a semester off and wanted to graduate in 4 years.)