Answer:
The number of mollies fishes in the aquarium is 20 .
Step-by-step explanation:
Given as :
The capacity of aquarium = 40 gallons
∵ 1 gallon = 4 quart
∴ 40 gallons = 4 × 40 = 160 quart
Now, According to question
0.25 inches of fish required 1 quart capacity
I.e for 1 quart capacity , 0.25 inches fish
So. for 160 quart capacity , 0.25 × 160 = 40 inches fishes
Now the size of mollies fish = 2 inches
Then , number of mollies fish = 
I.e Number of mollies fish =
= 20
Hence The number of mollies fishes in the aquarium is 20 . Answer