Hi could someone help me set up an equation for this problem

At noon, a train leaves city B heading east at 90 mi/h to city C 450 mi away. At 12:15 pm, a train leaves city C heading west to city B at 100 mi/h. At what time will they pass each other?

Hints: How far did the one train go in the first fifteen minutes? So what distance remains to be covered? What is the speed (in "mph") at which the two trains approach each other? How long would it take, at that speed, to cover the remaining distance?

If you get stuck, please reply showing how far you have gotten.