Answer:
-19x^2 + 2x - 1 is your answer.
Step-by-step explanation:
All you do is add the ones that are matching.
(-3x+8-7x^2)+(5x-9-12x^2)
-3x + 5x = 2x
8 - 9 = -1
-7x^2 - 12x^2 = -19x^2
