Let number of passengers in second car in d line train =x
Number of passengers in first car of a d line train in beginning = 1.5 x
Now at newton center
Number of passengers in first car of a d line train =1.5 x-3
Number of passengers in second car of a d line train= x +2
But after this stop both car have equal number of passengers.

So we get x=10
So number of passengers in first train at beginning =

number of passengers in second train at the beginning=10