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

[Q]: A new building needed 12 windows . The builder had already installed 6 of them . If it takes 4 hours to install each window , how long will it take him to install the rest ?
[A]: 24

[Q]: Tom had to wash 10 short sleeve shirts and 25 long sleeve shirts before school . If he had only washed 5 of them by the time school started , how many did he not wash ?
[A]: 30

[Q]: Rachel was organizing her book case making sure each of the shelves had exactly 9 books on it . If she had 6 shelves of mystery books and 2 shelves of picture books , how many books did she have total ?
[A]:
72