You are given a math word problem and you are supposed to only use subtraction on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

Example input: Context: Sam is 6 feet tall and Alex is 5 feet tall 

 Question: By how many feet is Sam taller than Alex? 
Example output: 1
Example explanation:  Sam's height - Alex's height = 6-5 = 1
Q: Context: Paul had 71 books. After selling some in a garage sale he bought 38 new ones. If he has 116 books now 

 Question: How many more books did he buy than he sold?
A:
45