Hello there!
To start off this problem, let's replace f(x) with x in the equation. This gives us the following.
[tex]x= \dfrac{3}{4} x+12[/tex]
Subtract 3/4*x from both sides.
[tex]x- \dfrac{3}{4} x=12[/tex]
[tex] \dfrac{4}{4} x-\dfrac{3}{4}x=12[/tex]
[tex] \dfrac{1}{4} x=12[/tex]
Now, multiply both sides by 4 to eliminate the fraction on the left side.
[tex]x=12*4=48[/tex]
Your answer is B. Hope this helps! :)
