Use the Distributive Property to Simplify. However, to make it easier, write out the equation like this. -1(-7y+12) This makes it so it simplifies to 7y-12.
In front of the negative their is an invisible 1 and that invisible 1 is the one your going to do distributive property with and then get a positive 7 because a negative divided by a negative is a positive.Your going to do the same thing to the twelve and then your answer is going to be 7y-12
