Answer:
Explanation:
The question is basically saying that f is equal to

when f=8, g=81. Therefore 8=
.
Then the next step is to simplify the equation, so k = 72.
The next step is to plug k=72 back into the original equation.
f=

Then you do the last step which is to plug f=4 into the equation which will result in 4=72/sqrt(g) => 4*sqrt (g) =72. Therefore sqrt (g) = 72/4 = 18. Then you square both sides and you get g=324.