What is the answer when subtracting (-3y2-+1)?

You have to distribute the minus sign to the second parenthesis, changing the sign of every term:

∠R = ∠Q, AS = AT       Given

∠5 = ∠6                        Base ∠'s of isosceles triangle are =

∠4, ∠5 are supplementary and ∠6, ∠7 are supplementary           Exterior sides in opposite rays

∠4 = ∠7                         Two ∠'s supplementary to equal ∠'s are =

Triangle RAS congruent to Triangle QAT          AAS

RS = QT                          CPCTE