The courses I've taken are algebra, trig, calculus 1 and 2 with analy. geometry and elementary linear algebra. Now that I have a three month break I plan on reviewing calc 1 and 2, and linear algebra. I would also like to learn a new topic but I dont know what subjects would be in my range of experience. I was thinking discrete math or set theory. Would those topics be difficult to learn on my own? Suggestions on other topics are welcomed.