The task is to generate the correct answer for a given math problem.

[EX Q]: Problem: what decimal fraction is 90 ml of a litre ?
[EX A]: . 09

[EX Q]: Problem: by selling an article for $ 195 , a person gains $ 45 . what is the gain % ?
[EX A]: 30 %

[EX Q]: Problem: john traveled 80 % of the way from yellow - town to green - fields by train at an average speed of 80 miles per hour . the rest of the way john traveled by car at an average speed of v miles per hour . if the average speed for the entire trip was 70 miles per hour , what is v in miles per hour ?
[EX A]:
6