Advanced Algebra Help Please?

Each hour the faster hiker gains 2 miles on the slower, and the slower had a 2 mile head start. So after 1 hour, the faster caught the slower. After 2 hours he was 2 miles ahead; after 3 hours, 4 miles ahead; after 4 hours, 6 miles and he needs one more mile so another half hour. Total hours for faster hiker = 4 1/2 hours meaning the slower went 5 1/2 hours. So what time is 5 1/2 hours before 4:00 PM is the answer so just figure that out.