Teacher: 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.
Teacher: Now, understand the problem? If you are still confused, see the following example:
Context: Sam is 6 feet tall and Alex is 5 feet tall 

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

Now, solve this instance: Context: A grocery store had 22 bottles of regular soda and 61 bottles of diet soda. 

 Question: How many more bottles of diet soda than regular soda did they have?
Student:
39