This document discusses linear equations using one or two variables. It defines a linear equation as having one or two variables, with no variables raised to a power greater than 1. Linear equations graph as straight lines when the pairs of values that satisfy the equation are plotted on a coordinate grid. The general form of a linear equation using two variables is presented as ax + by + c = 0, where a, b, and c are real numbers, a and b cannot both be 0, and c is a constant. Simultaneous equations are also introduced as two equations with the same two unknowns that must be solved together.