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.
--------
Question: Problem: if a / b = 4 / 3, then ( 3 a + 2 b. / ( 3 a - 2 b. = ?
Options: a. 6, b. 3, c. 5, d. - 1, e. none

Answer: b


Question: Problem: excluding stoppages, the average speed of a bus is 60 km / hr and including stoppages, the average speed of the bus is 40 km / hr. for how many minutes does the bus stop per hour ?
Options: a. 18 min, b. 17 min, c. 19 min, d. 20 min, e. 21 min

Answer: d


Question: Problem: working together, wayne and his son can shovel the entire driveway in three hours. if wayne can shovel six times as fast as his son can, how many hours would it take for his son to shovel the entire driveway on his own ?
Options: a. 4, b. 6, c. 8, d. 7, e. 12

Answer:
d