Stacy eats 2/3 of pizza on Monday. She eats the rest the next day. How much of the pizza did she eat?

The whole thing.

If theres 3/3 of pizza and she ate 2/3 on Monday and then ate the rest the next day, she ate the whole thing.

Let's evaluate:

2/3 - Monday

1/3 - Tuesday

3/3 - Altogether

1/3 + 2/3 = 3/3 = 1

1 whole pizza.

The whole pizza