Some good links have been posted. I'll post another, but it's just the first link I saw for what it is I think you should learn first: the Distributive, Associa

Some good links have been posted. I'll post another, but it's just the first link I saw for what it is I think you should learn first: the Distributive, Associative, and Commutative Laws. They're taught in middle school, and easy to get. But you need to get them _deeply_. Spend hours internalizing them. Play around in a spreadsheet, making 2 or 3 formulas at a time that all do the same calculation but look different because you distributed, associated, and commuted the cell addresses differently in the formulas. Learn them so well you might forget the names but you can't forget the concepts, ever. Make them part of your being. https://www.mathsisfun.com/associative-commutative-distributive.html https://www.mathsisfun.com/associative-commutative-distribut...