<human>:  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?
<bot>: How many cartons of berries did Emilia have before going to the supermarket? ** She previously had 2 cartons + 7 cartons = <<2+7=9>>9 cartons of berries.
How many cartons of berries does Emilia need to buy? ** Emilia needs to buy 42 cartons - 9 cartons = <<42-9=33>>33 cartons of berries.
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