IGHT im pretty stupid right now but can you help me out?

For a function f(x), a) if f(7) = 22 then f^-1(22) = b) f^-1(f(c)) =

The graph shows the decibel measure for sounds depending on how many times as intense they are as the threshold of sound. noise in a quiet room is 500 times as intense as the threshold of sound. what is the decibel measurement for the quiet room? 20 decibels28 decibels200 decibels280 decibels

Is (root2 -2)^2 rational or irrational. show the steps and answer fast