Question

Given f(x) = 2x + 9, if f(x) = 15, find x.​

Answer 1

if f(x) = 15, then rewrite the equation replacing the f(x) with 15

15 = 2x + 9

subtract 9 from sides

15 - 9 = 6

9 - 9 = 0

then, you would be left with 6 = 2x

divide by 2 on both sides

6/2 = 3
2x/2 = x

x would be 3 :)