(-7x^9 +12x^6 -12)-(5x^9 +4x^6 -9)

-7x^9 +12x^6 -12-5x^9 -4x^6 +9

-7x^9-5x^9 +12x^6-4x^6 -12+9

-12x^9+8x^6-3