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.

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


[Q]: Problem: three 6 faced dice are thrown together. the probability that exactly two dice show the same number on them is
Options: a. 5 / 15, b. 5 / 12, c. 5 / 19, d. 5 / 12, e. 5 / 11
[A]: b


[Q]: Problem: a bus trip of 660 miles would have taken 1 hour less if the average speed v for the trip had been greater by 5 miles per hour. what was the average speed v, in miles per hour, for the trip ?
Options: a. 40, b. 45, c. 50, d. 55, e. 60
[A]:
d