You are given a math word problem and you are supposed to apply a single mathematical operator 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.

the roller coaster at the state fair costs 6 tickets per ride . if 8 friends were going to ride the roller coaster how many tickets would they need ?
48

bobby has 142 books . kristi has 78 books . what 's the difference of the number of bobby 's books and kristi 's books ?
64

victor had 9 books . during the book fair he bought 3 more . how many books did victor have total ?
12