Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.
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Question: Problem: a can finish a work in 60 days, b in 9 days and c in 2 days, b and c start the work but are forced to leave after 3 days. the remaining work was done by a in ?
Options: a. 10 days, b. 25 days, c. 6 days, d. 7 days, e. 8 days

Answer: b


Question: Problem: if 9 / ( 1 + 4 / x ) = 1, then x =
Options: a. 3, b. 1 / 2, c. 1 / 3, d. - 1 / 3, e. - 3

Answer: b


Question: 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 ?
Options: a. 30, b. 40, c. 50, d. 55, e. 60

Answer:
e