The height of the ball initially is 54 inches. The common ratio has been provided which is 0.750.
The explicit formular for the geometric sequence is shown as;

The explicit formula is shown as;
54 x (0.750)^9
The rest is simply to solve for the height on the 10th bounce
Given that the number of years should be represented with x, the number of fish in the pond after x years should best be represented with f(x). The equation that would best show the given scenario in the problem above is,
f(x) = 500(2^x)
From the given, 500 is used as the initial population of the fish.
next month she will earn 4943.25 !
Is there more to this problem? By saying f(4), you'd be inputting a 4 for every variable x. There is not enough info here to answer the question.