A variable is usually a letter that is put in an equation to represent an unknown number. For example, in the equation 1+x=2, the variable is x. To solve for x, we need to get x alone on one side, and that means getting rid of 1. This can be done using subtraction, 1-1+x=2. However, what we do on one side of the equation we must do on the other, so subtract 1 from 2 as well, x=2-1. The end result is x=1.
