Question

Mary opened a 1-qt carton of milk. She drank 1 c of it. How many cups of milk were left?

Answer 1

3 cups.

Explanation:

In a quart, there are 4 cups. If Mary drank one of those cups, it would be the same as the equation `4-1`. So, since 4-1 is equal to `3`, there is 3 cups of milk left.