I need help on this question!??

The only thing you will do is to plug the x in the equation.

x = -2 ---> f(x) = -6

x = 0 ---> f(x) = 0

x = 3 ---> f(x) = 9

x = 7 ---> f(x) = 21

f(x) = 3x

f(-2) = 3(-2)

f(-2) = -6

f(0) = 3(0)

f(0) = 0

f(3) = 3(3)

f(3) = 9

21 = 3x

21 / 3 = 3x / 3

7 = x

Hope this helps, thank you :) !!

i have no clue what you just said. write a question in english?