A can complete a task in 15 hours, B can complete it in 10 hours, and C can complete it in 6 hours. If all three work together, how long will it take to complete the task?
Answer: C. 3 hours
The combined work rate is 1/15 + 1/10 + 1/6 = 1/3. Therefore, they will complete the work together in 3 hours.