Answer
15 mi/h; 30 mi/h
Work Step by Step
Since the are 90 mi apart and meet in 2 hours, their combined speed is $\frac{90mi}{2h} = 45 mi/h$. Let the speed of the slower cyclist be x. The speed of the faster cyclist is then 2x. We can then say that $x+ 2x = 45$, since their combined speed is 45 mi/h. Solving for x, we can see that the slower cyclist goes 15 mi/h and the faster cyclist goes 30 mi/h.