Answer:
x = 3
Step-by-step explanation:
f(x) means function of x, and could be replaced by y to just give a y = mx + b equation. So if f(x) = y = 11, you're pretty much solving for x with the equation
11 = 3x + 2
From there, isolate x, and you have your answer.
11 = 3x + 2
9 = 3x
x = 3
