Susan has 3 fish tanks to fill. 1 fish tank contains 7 goldfish and 8 beta fish. The second fish tank contains twice as many fish as the first tank and the third fish tank has a third of the number of fish in the second fish tank. How many fish are in the third fish tank?
Let's think step by step.
10
In the first fish tank, there are 7 goldfish + 8 beta fish = 15 fish.

The second fish tank therefore has 15 fish in the first tank * 2 = 30 fish.

So the third tank has 30 fish in the second fish tank / 3 = 10 fish.

.

Thus, the answer is 10