Let the speed of one rider = x
The speed of the second rider would e 2x ( twice as fast)
The total speed of the two riders would be x + 2x = 3x
Speed = Distance / time
Using the numbers:
3x = 72/3
Simplify:
3x = 24
Divide both sides by 3:
x = 8
The speed of one rider is 8 miles per hour
The speed of the second rider is 2(8) = 16 miles per hour.