You are given a math word problem and you are supposed to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the following question and then only report the final numerical answer.
Example: Last year , 90171 people were born in a country , and 16320 people immigrated to it . How many new people began living in the country last year ?
Example solution: 106491
Example explanation: Total people living in the country = born - immigrated = 90171 - 16320 = 106491

Problem: The school cafeteria had 23 apples . If they used 20 to make lunch for the students and then bought 6 more , how many apples would they have ?

Solution: 9