The Art of Problem Solving, affectionately known as “AoPS” for short, is a math program offering books and courses covering high-school mathematics from an advanced and challenging perspective. The heart of AoPS is a two-volume set of books, mentioned before in “Resources for Math Learning (Intro to Math)”: The Art of Problem Solving, Volume 1: the Basics by Sandor Lehoczky and Richard Rusczyk (solutions) The Art of Problem Solving, Volume 2: and Beyond by Richard Rusczyk and Sandor Lehoczky (so...