You are given a math word problem and you are supposed to apply a single mathematical operators like addition, subtraction, multiplication or division on the numbers embedded in the text to answer the following question and then only report final the numerical answer.

18 children were riding on the bus . At the bus stop , some more children got on the bus . Then there were 25 children altogether on the bus . How many children got on the bus at the bus stop ?
7

Ellen went to a garage sale to buy chairs . Each chair is 15 dollars . How much did Ellen spend for the 12 chairs she bought ?
180

Joan found 79 seashells on the beach , she gave Mike 63 of the seashells . How many seashells does she now have ?

16