Please help me don’t have that much time please and thank you

[tex]f(x)=\frac{1}{9}x-2\\ take:\\x=f(x)^{-1}\\\\f(x)=X\\\\X=\frac{1}{9}f(x)^{-1}-2\\\\(X+2)9 =f(x)^{-1} \\\\f(x)^{-1}=9X+18\\[/tex]