Answer:
28 minutes
Step-by-step explanation:
Speed = distance / time
Your speed is 1 lawn / 57 minutes. Your friend's speed is 1 lawn / 54 minutes. Working together, your combined speed is:
1/57 + 1/54
So the time it takes working together is:
Speed = distance / time
1/57 + 1/54 = 1 / t
t = 27.7 minutes
Rounded to the nearest whole number, it takes 28 minutes.