Roslyn has twenty boxes. Thirteen of the boxes contain pencils, nine of the boxes contain pens, and three of the boxes contain neither pens nor pencils. How many boxes contain both pens and pencils?
<|im_start|>system
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<|im_start|>user
Roslyn has twenty boxes. Thirteen of the boxes contain pencils, nine of the boxes contain pens, and three of the boxes contain neither pens nor pencils. How many boxes contain both pens and pencils?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
5
Roslyn has twenty boxes. Thirteen of the boxes contain pencils, nine of the boxes contain pens, and three of the boxes contain neither pens nor pencils. How many boxes contain both pens and pencils?
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