This is a composition of functions
We have f(x)=2x+7 and g(x)=3x+12
(g o f) = g(f(x))=g(2x+7)= 3(2x+7)+12=6x+21+12=6x+33
When we replace x=-6 in the (g o f) =6x+33 we get
(g o f)(-6) =6*(-6)+33= -36+33= -3
Good luck!!!
