The following are the ages (years) of 5 people in a room:
20, 21, 20, 21, 21
A person enters the room.
The mean age of the 6 people is now 20.
What is the age of the person who entered the room?

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. create a question you could ask that could be answered only by graphing or using a logarithm.