Question 255262
Let the speed of Bob = x
Given, Mark travels 4 miles an hour slower than Bob
So the speed of Mark = x-4
Bob reaches Asheville which is 60 miles away and at once turns back, meeting Mark 12 miles from Asheville.
Therefore the time taken by Bob to travel 72 miles is equal to the time taken by Mark to travel 48 miles 
            72/x = 48/(x-4)
            72(x-4) = 48x
Dividing by 24, we get
             3(x-4) = 2x
             3x-12 = 2x
             3x-2x = 12
                 x = 12
Therefore,the speed of Bob  = 12 miles/hr
          the speed of Mark = 12-4 = 8 miles/hr