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

Q: Context: Marco and his dad went strawberry picking. Together their strawberries weighed 20 pounds. His dad's strawberries weighed 17 pounds. 

 Question: How much did marco's strawberries weigh?

A: 3
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Q: Context: 43 children were riding on the bus. At the bus stop some children got off the bus. Then there were 21 children left on the bus. 

 Question: How many children got off the bus at the bus stop?

A: 22
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Q: Context: Rachel had to complete 7 pages of math homework, 11 pages of reading homework and 8 more pages of biology homework. 

 Question: How many more pages of reading homework than biology homework did she have?

A:
3
****