I am not doing the entire problem, I just do part of it.
At 10:00 AM the Van and Car are that the same place. After 2 hours the Car catches up to the Truck. Now, before those two hours the Truck was some distance ahead of the car/van call that . Thus, the distance the car traveled in those two hours is the distance the trucked traveled plus . Thus,
But we know what the speeds are thus,
That means the distance from the car/van at 10:00 to the truck was 80 kilometers.
The problem says that at 6pm (after 8 hours) the van overtakes the truck. That means, the the distance the van traveled from 10:00AM to 6:00PM is the same as the distance the truck traveled plus the distance is was already ahead-which we found to be 80.
Since we know the speed of the truck (divide by eight),
Thus, the speed of the van is 90 kilometers per hour.