Answer: 20 lawns could be mowed in 35 hours.
Step-by-step explanation: Lets write a ratio to represent this problem. The ratio 7:4 states that for every 7 hours you will mow 4 lawns.
Now we have to figure out how many lawns we will mow in 35 hours. Simply keep adding 7 to the left side of the ratio and 4 to the right side.
7:4
14:8
21:12
28:16
35:20
So in 35 hours, 20 lawns will be mowed.