Question 26006
Use the distance formula: {{{d = rt}}} where: d = distance traveled, r = rate of travel (speed), and t = time of travel.

For the east-bound plane: d1 = 550 mph(t)
For the west-bound plane: d2 = 500 mph(t)

But: d1 + d2 = 2100 miles, so:
550(t) + 500(t) = 2100  Solve for t.
1050(t) = 2100 Divide both sides by 1050
t = 2 hours.