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.

[EX Q]: last thursday drew had $ 30 . over the weekend he received some money for cutting the grass . he now has $ 61 . how much money did he get paid for cutting the grass ?
[EX A]: 31

[EX Q]: 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 ?
[EX A]: 30

[EX Q]: the next museum on her list is the guggenheim in new york as well . there she gave 51 sets of egyptian mask from her collection of 90 how many sets of masks were left in alicia 's collection ?
[EX A]:
39