Though you are required to understand differentiating from first principles for the exam, questions such as this become quite straightforward once you know the trick.
To differentiate all you have to remember is:
Multiply by the power and reduce the power by 1. (subtract 1 of the power)
So the answer for this question is 3x3-1 + 6x1-1+ 0 (As 1 is the same as x^0)
Hence the answer is 3x2+6