Answer :
Remember the following property of invertible functions:
[tex]f(x)=y\qquad\Leftrightarrow\quad f^{-1}(y)=x[/tex]Then:
[tex]f^{-1}(f(x))=x\qquad\forall x[/tex]Then:
[tex]f^{-1}(f(7))=7[/tex]Therefore, the answer is: 7.
Remember the following property of invertible functions:
[tex]f(x)=y\qquad\Leftrightarrow\quad f^{-1}(y)=x[/tex]Then:
[tex]f^{-1}(f(x))=x\qquad\forall x[/tex]Then:
[tex]f^{-1}(f(7))=7[/tex]Therefore, the answer is: 7.