Answer: he had a better pay when he mowed his neighbor's lawn.
Explanation:
Two weeks ago he mowed a neighbor's lawn for half an hour and earned $10. This means that the amount that he would earn per hour is
10/0.5 = $20
Last week he mowed at his uncle's lawn for 3 1/2 hours and earned $30. This means that the amount he would earn per hour is
30/3.5 = $8.6
This week he mowed the lawn of a community center for 2 hours and $30. This means that the amount he would earn per hour is
30/2 = $15
Therefore, he had a better pay when he mowed his neighbor's lawn.