It is important to keep a close eye on all the information’s that are given in the question. Based on those given information’s the answer can be easily deduced.
The distance traveled by Linda in 3 hours = 4.8 miles
Then
In 1 hour the distance traveled by Linda = (4.8/3) * 1 miles
= 1.6 miles
So the speed of Linda is 1.6 miles per hour. I hope the procedure is simple enough for you to understand. You can always solve similar kind of problems using this simple procedure.