Samantha drove 168 miles in 3 1/2 hours. She then drove the next 2 1/4 hours at a rate of 5 miles an hour faster than the first rate. How many miles did Samantha drive during the 5 3/4 hours?

First you want to find the first speed. Speed=distance/time so it's 168/3.5=48. You know for the next period of time she drives 5 mph faster so that speed is 53 mph. Now you want to find distance which is speed x time. So 53 x 2.25 which is 119.25. You now have the second distance so you add it to the first, 119.25+168=287.25 miles