You want to find out how much flour she used first. In order to do that, you want to convert all your givens, into the same denominator so you can add them together.
For 2/5, multiply the top and the bottom by 2.
2/5 = 4/10 she uses for pizza.
3/10 already has the same denominator, so we can add them together.
4/10 for pizza + 3/10 for bread = 7/10 already used.
1- 7/10 = 3/10 left
