Hi there!
The answer is:
[tex]3x ( x+3)(x-2)[/tex]
To find our answers we need to find out which terms are in common.
[tex] 3x^{3} = 3 * x* x*x \\ 3 x^{2} = 3*x*x \\ 18x = 3*6*x[/tex]
Now we can easily see that '3' and 'x' are in common. Therefore, we can bring those outside the parenthesis. The other terms will be positioned between parenthesis.