Final answer:
Clark is the faster lawn mower, with a rate of 0.833 lawns/hour compared to John's rate of 0.75 lawns/hour.
Step-by-step explanation:
To determine who is faster between John and Clark in mowing lawns, we need to calculate their rates of mowing. John can mow 3 average-sized lawns in 4 hours, while Clark can mow 5 average-sized lawns in 6 hours.
To find their rates, we divide the number of lawns each can mow by the number of hours it takes them. John's rate is 3 lawns/4 hours = 0.75 lawns/hour, and Clark's rate is 5 lawns/6 hours = 0.833 lawns/hour.
Comparing the two rates, we see that Clark is faster because he can mow more lawns per hour than John can.