We are given the linear function below:
[tex] \large{f(x) = 3x + 13}[/tex]
To find f(4), simply substitute x = 4 in the equation.
[tex] \large{f(4) = 3(4) + 13} \\ \large{f(4) = 12 + 13} \\ \large \boxed{f(4) = 25}[/tex]
Answer