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

[Q]: Will invited 9 friends to a birthday party , but 4 could n't come . If he wanted to buy enough cupcakes so each person could have exactly 8 , how many should he buy ?
[A]: 40


[Q]: 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 ?
[A]: 180


[Q]: Mrs. Hilt saw a rollercoaster . 7 students rode the rollercoaster every 5 minutes . How many students rode the rollercoaster in 15 minutes ?
[A]:
21