15.simplify the expression below. show your work. +12)

The simplified expression of -(-7y+12) is (7y - 12). In simplifying expressions, we  just need to multiply the variable inside the parenthesis by the variable outside. In this case, negative sign outside the parenthesis is not just a negative but rather it means that it is negative 1 or -1. It is always assumed that when there is no numeric value on the sign the value of which is one.

They are the facts that mary is a citizen