A pet store has three fish tanks, each holding a different volume of water and a different number of fish. Tank A holds 40 L and 5 fish. Tank B holds 100 L and 12 fish. Tank holds 180 L and 23 fish,
Order the tanks by volume per fish from least to greatest

For each tank just divide the number of L by the number of fish to get the volume or fish.

For tank A it is 40/5=8, for tank B it is 100/12=8.3, and for tank C it is 180/23=7.8.

If you number them least to greatest, it is (tank C, tank A, tank B)

a = 11 : 4

b = 38

c = 1 for every 6