Answer:
$644
Step-by-step explanation:
if the lawn is 15 yards wide and 31 yards tall, you need to figure out the perimeter. 15+15+31+31=92, so the perimeter of the yard is 92 yards. If it costs $7 per yard, then all you need to do from there is multiply 92 by 7, getting you 644. So it would cost $644 to install a fence around the lawn.