Combining like terms is used in math in order to simplify expressions. We combine common terms in order to make the expression much easier. Common terms are those that have the same variable and exponent. So in the expression:

so to figure this out, we need to simply divide 6,688 people by 7.267 square miles. 6,688/7.267=920.324.... So we have approximately 920.324 people per square mile