-(-7y + 12) = 7y - 12
u are distributing the -sign through the parenthesis...so u take the number outside of the parenthesis (and if it just a sign, the number is 1)...and u multiply it by everything in the parenthesis.
-1(-7y + 12) = -1 * -7y + (-1) * 12 = 7y + (-12) = 7y - 12
