Question 128590
{{{f(x)=20000-15x}}} Start with the given function



To find {{{f^(-1)(x)}}}, simply swap x and f(x) to get 


{{{x=20000-15f(x)}}} 



{{{15f(x)+x=20000}}} Add 15f(x) to both sides



{{{15f(x)=20000-x}}} Subtract x from both sides



{{{f(x)=(20000-x)/15}}} Divide both sides by 15 to isolate f(x)



So the inverse function is {{{f^(-1)(x)=(20000-x)/15}}} 



{{{f^(-1)(50)=(20000-50)/15}}} Now plug in {{{x=50}}}



{{{f^(-1)(50)=(19950)/15}}} Subtract



{{{f^(-1)(50)=1330}}} Divide