Some bank robbers leave town, speeding at 75 75 mph. ten minutes later, the police give chase, traveling at 81 81 mph. how long will it take the police to catch up to the robbers (round to the nearest hundredth hour)?

The robbers have a 10 minute head start. 
In 10 minutes (1/6 of an hour) at 75 mph you can travel
75 * (1/6) = 12.5 miles
Now we have to see how long it takes to travel 12.5 miles at 81 mph.
12.5 / 81 =  0.1543209877 hours
which rounds to 0.15 hours
 
which equals
0.1543209877 * 60 = 9.2592592593 minutes

What does h hours mean