Write as an algebraic expression: *20% of 75% of y

Show algebraically that f and g are inverse functions f(x)=x^2/-6; g(x)=square root of 2x+12

News cameras take an overhead picture of a crowd at an outdoor event journalist then count the total number of people in the picture and use the sample of estimate the total number of people in the crowd this process is an example of

Ineed if you could explain and give me the answer you! this needs done