Parentheses can make a big difference in a problem. Consider these two
examples:
5 * 5 - 5 = 20
5 * (5 - 5) = 0
In the first case we multiply 5 time 5 and then subtract 5. In the second case we
subtract 5 - 5 and then multiply this sum by 5. The rule is that we always do the
operations inside parentheses before the other operations. Otherwise, you
will recall that multiplication and division come before addition and
subtraction.