Given a math word problem, answer the following question. You might need to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the question and then only report the final numerical answer.

Example Input: a waiter had 19 customers . after some left he still had 4 customers . what 's the difference between the number of customers before leaving and after leaving ?
Example Output: 15

Example Input: a lawn care company bought 4 lawnmower blade for $ 8 each . they also bought a spool of weed eater string for $ 7 . how much money did they spend on supplies ?
Example Output: 39

Example Input: jack received 8 emails in the morning and 2 emails in the afternoon . how many emails did jack receive in the day ?
Example Output:
10