You are given a math word problem and you are supposed to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

Q: Bobby has 142 books . Kristi has 78 books . How many more books does Bobby have than Kristi ?

A: 64
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Q: Donna weighs 69 pounds . Willie weighs 51 pounds . How much heavier is Donna than Willie ?

A: 18
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Q: Lana was unboxing some of her old winter clothes . She found 3 boxes of clothing and inside each box there were 3 scarves and 4 mittens . How many pieces of winter clothing did Lana have total ?

A:
21
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