## Algebra 1: Common Core (15th Edition)

In order to solve this algebraic expression, we must isolate the variable. A variable is the letter in the problem (for instance, in the equation x+2=10, x is the variable). Because addition and subtraction are inverse operations (they cancel each other out), we know we must add when a number is being subtracted from the variable and subtract when a number is being added to the variable. In the equation x-4=-2, we must get rid of the 4, which is on the same side as x, in order to solve. Thus, we add 4 to both sides of the equation to find that x=2. When we plug in our calculated value for x into the initial equation, we find that $-2=-2$, so the answer that we found is correct.