
That is an equation. What is the question?

I need to rewrite the function of x in the equation 3x+4y=11

Is f(x) = 3 over 4x + 11 over 4 the correct answer? 3 over 4 is a fraction and 11 over 4 is a fraction.

You want y = f(x)
4 y = 11 + 3x
y = f(x) = (3/4)x + 11/4
now you have y alone on the left and a function of x on the right.