Answer
$$8x^3 +7x^2+11x$$
Work Step by Step
In order to solve this problem, it is necessary to combine like terms.
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.
Also, note that with subtraction problems, it is necessary to distribute the negative to all terms within the parenthesis.
Thus, combining like terms, we obtain:
$$8x^3 + (12-5)x^2 +(9+2) x \\ 8x^3 +7x^2+11x$$
