The correct answer is -13x2 - 10x + 12. The negative is distributed inside the parentheses first to get 3x3 - 7x2 + 12 - 3x3 - 6x2 - 10x. The 3x3 and - 3x3 cancel each other. The - 7x2 and - 6x2 combine to give you -13x2. The -10x is alone. The 12 is alone.
