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: Mary has 9 yellow marbles . Joan has 3 yellow marbles . How many yellow marbles do they have in all ?

A: 12
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Q: There are 38 books on the shelf . Marta put 10 more books on the shelf . How many books are on the shelf now ?

A: 48
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Q: Luke had 48 dollars in January . By March he had spent 11 dollars . If he got another 21 dollars from his mom , how much money would he have ?

A:
58
****