Two airplanes leave phoenix at the same time and fly in oppo

Two airplanes leave phoenix at the same time and fly in opposite directions. One plane travels 60 miles per hour faster than the other. After 2.5 hours they are 1700 miles apart. What is the rate of the slower plane?

One does X mph, the other x + 60 mph
Total is thus 2X + 60 mph
After 2.5 hours, they are 2.5(2X + 60) miles away, which is 1700
5X + 150 = 1700
5X = 1550
x = 310 mph, the other does 370 mph