Answer: 4
Step-by-step explanation:
The procedure is pretty basic. First you have to substitute what you know in the equation. So as you know f(x)=18, just substitute f(x) by 18, leaving it like 18 = 3x + 6.
Then you have to start to move things around. First start with the + 6 that is adding, so it moves to the other side as a substraction giving 18 - 6 = 3x -> 12 = 3x. The next step is to get rid of that 3, so because it's multiplying the x, it moves to the other side as a division leaving you with 12 ÷ 3 = x -> 4 = x. There you have the answer! For a value/y of 18 in that function, the x is 4
