Question 1009093
Traveling for 20 min (1/3 hr) at 48 mi/hr she traveled:
(1/3 hr)(48 mi/hr)=16 miles
If she continued to checkpoint 2 from checkpoint 1,
(sentence one in question), the distance between 
checkpoints was 16 miles, and she arrived at Checkpoint 2
20 minutes after she left Checkpoint 1. 
Giving broken up parts of a question does not allow a
complete answer. I hope this helps, but I mostly was
guessing at your intention. In the future, give the entire 
question to get the entire answer.