Please show me what i'm doing wrong

Question

 Let f (x) = 3x^2+ 7 and g(x) = x – 4.
 Find ( f o g)(− )1 . 

 

i've been working on this and my answer is 

(fog)(-1)=3x^2-22x+55

 

but i'm still getting it marked wrong. I don't know if i'm missing a step or not. 

Answer 1

(f º g)(x) = f(g(x)) = f(x-4) = 3(x-4)²+7

 

                                      = 3(x²-8x+16) + 7

 

                                      = 3x²-24x+55

 

So, (f º g)(-1) = 3(-1)²-24(-1)+55 = 82