Given a math word problem, answer the following question. You might need to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the question and then only report the final numerical answer.
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Question: cade had 87 marbles . he gave 8 to dylan . how many does he have left ?

Answer: 79

Question: upon finishing the treehouse charlie 's mother served them freshly baked cookies . if charlie ate 15 cookies his father ate 10 and his mother only ate 5 how many cookies were eaten in total ?

Answer: 30

Question: misha has 34 dollars . how many dollars does she have to earn to have 47 dollars to buy a dog ?

Answer:
13