Math homework please help ​

Create a question with this scenario you could ask that could be answered only by graphing or using logarithm. david estimated he had about 20 fish in his pond. a year later, there were about 1.5 times as many fish. the year after that, the number of fish increased by a factor of 1.5 again. the number of fish is modeled by f(x)=20(1.5)^x.

What adds to be the bottom number but also multiplies to be the top number with 8 on the bottom and 15 on top

Asequence is a function whose is the set of natural numbers