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?
In the first fish tank, there are 7 goldfish + 8 beta fish = <<7+8=15>>15 fish.
The second fish tank therefore has 15 fish in the first tank * 2 = <<15*2=30>>30 fish.
So the third tank has 30 fish in the second fish tank / 3 = <<30/3=10>>10 fish.
#### 10