Emilia needs 42 cartons of berries to make a berry cobbler. She already has 2 cartons of strawberries and 7 cartons of blueberries in her cupboard. She decides to go to the supermarket to get more cartons. How many more cartons of berries should Emilia buy?
She previously had 2 cartons + 7 cartons = <<2+7=9>>9 cartons of berries.
Emilia needs to buy 42 cartons - 9 cartons = <<42-9=33>>33 cartons of berries.
#### 33