A jet departs from an airport flying east. At the same time, a second jet departs from the same airport flying west at a speed of 20 mph slower than the first jet. After 1.5 hours, the planes are 1500 miles apart. What is the speed in miles per hour of the jet traveling east?
A - 300
B - 750
C - 510
D - 490
Speed × Time = Distance
Let x be the speed of the jet travelling East, in mph.
(x)(1.5) + (x-20)(1.5) = 1500
1.5x + 1.5x - 30 = 1500
3x = 1530
x = 510