Answer:
3 hours
Step-by-step explanation:
1/5 of an hour is 12 minutes.
So 1/15 of a lawn takes 12 minutes to water.
Next you multiply 15, how many times 1/15 of a lawn is watered, and multiply it by 12, the time it takes to water 1/15 of a lawn.
So you would get 180 minutes.
Finally you convert it to hours. To do this, you divide it by 60, how many minutes in and hour, and should get an answer of 3 hours.
Hope this helps!