Answer:
x=48
Step-by-step explanation:
f(x) is basically just another way to write y.
If f(x)=x, then y=x.
x=3/4x+12 (Original Equation Substituting x for f(x), equal to y)
1/4x=12 (Subtract 3/4 from both sides of the linear equation)
x=48 (Multiply both sides by 4)
