How do you do systems of equations? - Answers

There are several methods to do this; the basic idea is to reduce, for example, a system of three equations with three variables, to two equations with two variables. Then repeat, until you have only one equation with one variable. Assuming only two variables, for simplicity: One method is to solve one of the equations for one of the variables, then replace in the other equation. Another is to multiply one of the equations by some constant, the other equation by another constant, then adding the resulting equations together. The constants are chosen so that one of the variables disappear. Specifically for linear equations, there are various advanced methods based on matrixes and determinants.