Question 769678
Distance = Speed * Time
1)Distance = 80mi/hr * 3.5hrs
  Distance = 280mi
2)Distance = 10mi/hr * 2hrs
  Distance = 20mi
Total Distance = 300 miles.
....................
Speed = Distance/ Time
Speed = 300mi/5.5hrs
Average Speed = 54.55mi/hr
Hope this helps.
:-)