Respuesta :

Answer:

x = 1

Step-by-step explanation:

f(x) = 3x + 3

f(x) = 6

=> 3x + 3 = 6

=> 3x = 3

=> x = 1
f(6)=3(6)+3
f(6)=18+3
f(6)=21
you just have to substitute x with 6!:)