Since there is no x-term on the right side of the function, any value of x can be used to make f(x) = 12/16.
In fact, there is no way to make f(x) have any value but 12/16.
For instance: f(0) = 12/16, and f(1) = 12/16, and f(2.75) = 12/16, etc., for all values of x.