A bakery uses 70% of its milk in one week. They now have 36 quarts of milk left. The bakery started the week with how many quarts?

The bakery starts a week with 100% quarts of milk.
In the course of the week they use 70%, meaning the remainder is 30% quarts of milk.
Therefore, the remaining quarts are equivalent to 30%
thus,  36 = 30% to get 100% ;
     (36/30) ×100 = 120
Therefore, the bakery started the week with 120 quarts of milk