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.
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Question: John walks 0.7 miles to school and Nina walks 0.4 miles to school . How much farther does John walk than Nina ?

Answer: 0.3


Question: Mary had 8 potatoes in the garden . The rabbits ate 3 of the potatoes . How many potatoes does Mary now have ?

Answer: 5


Question: The school cafeteria ordered 42 red apples and 7 green apples for students lunches . But , if only 9 students wanted fruit , how many extra did the cafeteria end up with ?

Answer:
40