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.
One example is below.
Q: Context: Sam is 6 feet tall and Alex is 5 feet tall 

 Question: By how many feet is Sam taller than Alex? 
A: 1
Rationale:  Sam's height - Alex's height = 6-5 = 1
Q: Context: There are 11 different books and 17 different movies in the ' crazy silly school ' series. If you read 7 of the books and watched 21 of the movies 

 Question: How many more movies than books have you read?
A:
14