Answer:
9x^3-17x^2-x+7
Step-by-step explanation:
Distribute the negative you'll get
(12x^3-8x^2)+(-3x^3-9x^2-x+7)
Combine like terms
12x^3-3x^3=9x^3 , -8x^2-9x^2=-17x^2 , -x , +7
Putting it all together:
