You could just use your calculator thats on your phone of tab
The answer to the f(x) is D f(x) = 3x + 3 because (x,y) you input x into the equation and you get y, if that makes sens, u said u need it now so I won't go into it too much.
Answer:
C??????????????? ?????????
6*3 = 18
6*9 = 54
so 18 +54 is the correct answer