Answer: 
<em>Hi there! By my calculation, I got the answer above. However, it doesn't fit any one of the answer choices. I am not sure if I am totally correct, but I have been double-checking my answers. Please let me know whether it's the answer choices mistaken or I am wrong so that I could modify my answer if necessary.</em>
Step-by-step explanation:
<u>Given expression</u>
- (3x³ + x²) +2 (x³ - 4x²)
<u>Expand parenthesis by the distributive property</u>
= -3x³ - x² + 2x³ - 8x²
<u>Combine like terms</u>
= -3x³ + 2x³ - x² - 8x²

Hope this helps!! :)
Please let me know if you have any questions