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.

[EX Q]: At the schools book fair Sam bought 13 adventure books and 17 mystery books . If 15 of the books were used , how many new books did he buy ?
[EX A]: 15

[EX Q]: 179 birds were sitting in a tree . 38 more birds flew up to the tree . How many birds were there altogether in the tree ?
[EX A]: 217

[EX Q]: Adam has $ 5 to buy an airplane that costs $ 4.28 . How much change will he get ?
[EX A]:
0.72

