Acafeteria used 5 gallons of milk and preparing like how many 1 quart containers of milk did the cafeteria use

The cafeteria used 20, 1 quart containers. 

20 because there are 4 quarts in a gallon so 5 gallons*4 quarts per gallon

On monday,mrs.wise bought 3 lbs of apples at $4per lb= 4*3=$12on tuesday ,20%off and she buy 5 lbs of apples = $4-20%=3.20*5lb=$16example: other wise when she buy 5lbs on monday she have to spend 4*5=20