The speed of slower cyclist is 8 miles per hour
The speed of faster cyclist is 18 miles per hour
Solution:
One cyclist travels 10 min slower than the other
Let "x" be the speed of slower cyclist
Then, x + 10 is the speed of faster cyclist
The distance is given by formula:

Distance of slower cyclist =

Distance of slower cyclist = 4x
Distance of faster cyclist =

The two cyclists are 104 miles apart after 4 hours
4x + 4x + 40 = 104
8x + 40 = 104
8x = 104 - 40
8x = 64
x = 8
Thus rate of each cyclist is:
speed of slower cyclist = x = 8 miles per hour
speed of faster cyclist = x + 10 = 8 + 10 = 18 miles per hour