Question

Given ƒ(x) = 3x + 9, find x when ƒ(x) = 21.

Answer 1

3x + 9 = 21
3x = 12
x = 4

Answer 2

Answer:

4

Step-by-step explanation:

ƒ(x) = 3x + 9; Substitute 21 for ƒ(x).

21 = 3x + 9

21 − 9 = 3x

12 = 3x → x = 4