Answer:
5.5 miles
Step-by-step explanation:
The brother walks 3.5 miles in 1 hour. In half and hour, he walks half of 3.5 miles, or 1.75 miles.
The sister runs 7.5 miles in 1 hour. In half an hour, she runs half of 7.5 miles, or 3.75 miles.
Add the two distances:
1.75 miles + 3.75 miles = 5.5 miles
