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

 Question: By how many feet is Sam taller than Alex? 
Solution is here: 1
Explanation:  Sam's height - Alex's height = 6-5 = 1

Now, solve this: Context: There are 62 different movies and 19 different books in the ' crazy silly school ' series. If you read 4 of the books and watched 34 of the movies 

 Question: How many more books do you still have to read?
Solution:
15