Respuesta :

g(x) = 3x
g(x) = 3*( x )
g(f(x)) = 3*( f(x) ) ... every x has been replaced with f(x)
g(f(x)) = 3*( 3x ) ... replace the f(x) on the right side with 3x
g(f(x)) = (3*3)x
g(f(x)) = 9x