Answer:
55 feet per mile.
Explanation:
We have been given that you drive 8 miles from your house to your friends house. Your house is at an elevation of 240 feet. Your friend's house is at an elevation of 680 feet.
To find the mean change in elevation per mile, we will divide the difference of elevation by 8.



Therefore, the mean change in elevation per mile is 55 feet per mile.