Answer :
replace g(x) for x in f(x)
f(g(x))=-4(g(x))+7
f(g(x))=-4(10x-6)+7
f(g(x))=-40x+24+7
f(g(x))=-40x+31
f(g(x))=-4(g(x))+7
f(g(x))=-4(10x-6)+7
f(g(x))=-40x+24+7
f(g(x))=-40x+31