Two locomotives approach each other on parallel tracks. each have a speed of 95 km/h with respect to the ground. if they are initially 8.5km apart, how long will it be before they reach each other?

If they are both  traveling with the same speed that means that they will reach other in the middle of the line initially between them. In other word, each will have to travel the same amount before they reach other. 

Now you can calculate the time it takes for only one locomotive to travel half of the total distance between them, and that time is equal to the time you are looking for.

Use 
   t =  S1/2 / v

  where t-time, S-distance traveled , v-velocity