Answer :

naǫ
[tex]y=0.2x+1 \\ \\ \hbox{solve for x:} \\ y=0.2x+1 \ \ \ |-1 \\ y-1=0.2x \ \ \ |\times 5 \\ 5y-5=x \\ x=5y-5 \\ \\ \hbox{switch x and y:} \\ y=5x-5 \\ \\ \boxed{f^{-1}(x)=5x-5}[/tex]