Question 721589
freight train speed = x
passenger train speed = 50

freight train has traveled 6x miles before passenger train starts.

Catch up speed = 50-x

Catch up distance = 6x

time = 4

t= d/r

4= 6x/(50-x)

4(50-x) =6x

200-4x=6x

10x= 200
x= 20mph speed of freight train