Answer:
(x+2)(9x+6)
Explanation:
This is the whole process. Skip down to the bolded important part if you want.
Going to quickly expand it again:

This is in the form of:

To factor a trinomial in this form, you need to find 2 numbers that multiply together to make
, and also add together to make
.
In this case,

those 2 numbers are 18 and 6.
Then, in the above, expanded equation, you need to split b into 2 numbers, from 24 into 18 and 6.

Then, split the equation in half and factor each half individually.

Important part ==========
Now, we're right back at where we started with your question. All we need to do now is factor out the (x+2).

And you're done, that's all.