The correct option is :
<u><em>Explanation</em></u>
Suppose, the volume of the fish tank is ft³
The density of the fish tank is 0.5 fish/ft³. It means, <u>the number of fish in 1 ft³ volume is 0.5</u>
So, the number of fish in ft³ volume will be:
Given that, there are 30 fish in the tank. So, the equation will be......
Thus, the volume of the tank is 60 ft³