Respuesta :

f(x)=27 when x=9.  The point is then (9, 27).  If we switch places with x and y, we get (27, 9).   f-1(27) = 9
the inverse function of f(x) is f-1(x) = (1/3)(x).  Now you can find the answer, by substituting 27 into the formula for inverse.