He has 3 apples and 4 bananas, so he has 3 + 4 = <<3+4=7>>7 pieces of fruit.

He needs to buy 12 fruit - 7 fruit = <<12-7=5>>5 oranges.

# Answer

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<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Mark is looking to buy a total of 12 pieces of fruit at the store. He has already chosen 3 apples. He has also selected a bunch of bananas containing 4 bananas. How many oranges does he need to pick out to have 12 total pieces of fruit?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
5
Mark is looking to buy a total of 12 pieces of fruit at the store. He has already chosen 3 apples. He has also selected a bunch of bananas containing 4 bananas. How many oranges does he need to pick out to have 12 total pieces of fruit?
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