Answer:
3 hours
Step-by-step explanation:
Because first 3 friends have water that last 6 hours when you double the amount of people you get less water, I don't speak good English to explain but you have to subtract 3 from 6 because 3 is amount of people that need water that lasts 6 hours and when you have more people you get less water sooooo you subtract 3 from 6.
Hope you understand!
