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.

Zoe baked 5 brownies , but needed 11 total for her party . If she used 7 cups of flour on each one , how much cups of flour does she still need ?
42

Dave bought 12 boxes of chocolate candy and gave 5 to his little brother . If each box has 3 pieces inside it , how many pieces did Dave still have ?
21

A company invited 18 people to a luncheon , but 12 of them did n't show up . If the tables they had held 3 people each , how many tables do they need ?

2