Answer:
 1/7 hour
Step-by-step explanation:
Their closing speed is ...
 8 mph + 27 mph = 35 mph
Then the time it takes to cover 5 miles is ...
 time = distance/speed
 time = (5 mi)/(35 mi/h) = 1/7 h
The two will meet in 1/7 of an hour, about 8 minutes, 34.3 seconds.