Respuesta :

f(x) = (x + 9) / 3 and g(x) = 3x - 9

f((g)x) = (3x - 9 + 9) /3 = 3x /3 = x

g((f(x)) = 3 (x + 9)/3  - 9  = x + 9 - 9 =  x