Sherry and Bob like to jog in the park. Sherry can jog at 5 mph, while Bob can jog at 7 mph.
If Sherry starts 30 minutes ahead of Bob, how long will it take Bob to catch up to Sherry?
Let x = the time it takes Bob to catch Sherry
x + 1/2
5(x + 1/2)
Sherry started 30 minutes or 1/2 hour before Bob, so her time
must reflect that amount. Rate is in miles per hour, time must
be in hours so our units match.