How do I solve this? I keep getting the answer wrong.

Answer:
You start by mutliply 3 to every number in B
you get : 3 9 18 21 15 9 9 6 -15.
Multiply 2 to every number in C.
you get : 8 4 -6 6 6 0 10 12 6
Now you add the new numbers of B and the new numbers of C.
you get : 11 13 12 27 21 9 19 18 -9