Evaluating functions I don’t understand this one and I can’t find it no where else

The function given is
[tex]f(x)=4x[/tex]We are to find the inverse of the function
let f(x) =y
[tex]y=4x[/tex]Then, we make x the subject of the formula from here
[tex]\begin{gathered} y=4x \\ x=\frac{y}{4} \\ x=\frac{1}{4}y \end{gathered}[/tex]Then The inverse of the function becomes
[tex]f(x)=\frac{1}{4}x[/tex]Therefore the fourth option is correct