Answer:
135/x + 855/[3x] = 6
405 + 855 = 18x
x = 1260/18 = 70 mph
Step-by-step explanation:
let
x = time on the train
y = time on the plain
z = speed of the train
3z = speed of the plane
speed * time = distance
3zy = 855
y = 285 / z
xz = 135
x = 135 / z
total time was 6 hours
x + y = 6
(135 / z) + (285 / z) = 6
420 / z = 6
420 = 6z
70 = z
