Answer:
7
Step-by-step explanation:
I like to work liter volume problems in terms of decimeters. 1 dm = 10 cm, and 1 dm³ = 1 L, so the tank is 3 dm by 4 dm by 3 dm = 3×4×3 dm³ = 36 L.
36 liters will support 36/5 = 7.2 platies.
7 platies can be kept in the aquarium.