#### Answer

$f^{-1}(f^{-1}(1))$ = 2

#### Work Step by Step

First find where f(x) = 1. Since the function is one-to-one, f(6) = 1. Therefore $f^{-1}(f^{-1}(1))$ = $f^{-1}(6)$
Then find where f(x) = 6. Since the function is one-to-one, f(2) = 6. Therefore Therefore $f^{-1}(f^{-1}(1))$ = $f^{-1}(6)$ = 2