Answer
$$-\frac{x^3}{6}+4x^2-3$$
Work Step by Step
Recall, like terms must (1) be raised to the same power and (2) consist of the same variable (i.e. x and y are not like terms). It is also important to note that numbers are all like terms with each other when not multiplied by anything. Doing this, we find:
$$\frac{1}{6}x^3-\frac{1}{3}x^3+3x^2+x^2+7-10 \\ -\frac{x^3}{6}+4x^2-3$$
