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Math Preliminary Basic Mathematics by Serge Lang Buy/Pirate this book (he's dead). It's highschool math, from the perspective of a Mathematician. You will learn up Pre-Calculus and be prepared for rigorous proofs later. An Introduction to Mathematical Reasoning" by Peter J Eccels This changes you from rote drilling and being a human calculator in highschool to learning what math actually is, and what proofs do.