First, we have to open up the parentheses:
6x^3 + 18x^2 - 3x^2
6x^3 + 15x^2
There's not much else we can do other than factor, but it doesn't seem like factoring is necessary.
Simplify. Combine like terms.
6x^3 + (18x^2 - 3x^2)
6x^3 + 15x^2 is your answer
hope this helps
