What is the length of line segment fe?

enter your answer in the box. round to the nearest tenth.
fe = units

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.

3x = 729 solve for x plz . it's urgent. will mark

If x varies directly as y, and x = 7.5 when y = 10, find x when y = 4