Just need the reasons for the statements listed please!!

Iwant to know what 3g+5h+4g-2h is my teacher is too selfish to tell us

Acircular garden with radius of 8 feet is surrounded by a circular path with a width of 3 feet. what is the approximate area of the path alone? use 3.14 for π

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