Question 694392
1/6 + 1/9 = 1/t


3/18 + 2/18 = 1/t


5/18 = 1/t


5t = 18


t = 18/5


So it will take them 18/5 hours, or 3 and 3/5 hours (or 3.6 hours = 3 hours and 36 minutes) if they work together.