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.

[Q]: John walks 0.7 miles to school and Nina walks 0.4 miles to school . How much farther does John walk than Nina ?
[A]: 0.3


[Q]: Vanessa had 13 music files and 30 video files on her flash drive . If she deleted 10 of the files , how many files were still on her flash drive ?
[A]: 33


[Q]: Roger was putting his spare change into piles . He had 3 piles of quarters and 3 piles of dimes . If each pile had 7 coins in it , how many coins did he have total ?
[A]:
42