Answer:
[tex]{ \tt{f(x) = 69 - 15x}}[/tex]
• let's find the inverse function:
[tex]{ \tt{ m = 69 - 15x }} \\ \\ { \tt{15x = 69 - m}} \\ \\ { \tt{x = \frac{69 - m}{15} }} \\ \\ { \boxed{ \tt{f {}^{ - 1}(x) = \frac{69 - x}{15} }}} \\ [/tex]
• finally, let's find the function of the inverse function:
[tex]{ \tt{f( {f}^{ - 1}(x)) =69 - 15( \frac{69 - x}{15} ) }} \\ \\ { \tt{f( {f}^{ - 1}(x)) = 69 - (69 - x)}} \\ \\{ \boxed{ \boxed { \tt{ \: f( {f}^{ - 1}(x)) = x \: }}}}[/tex]
