The distance between the two villages is 540 km. A bus and a truck left these villages at the same time

The distance between the two villages is 540 km. A bus and a truck left these villages at the same time in the same direction, with the truck driving in front. In 18 hours the bus will catch up with the truck. What is the speed of a truck if the speed of the bus is 90 km / h?

Let’s calculate the speed of convergence between a bus and a truck:
540: 18 = 30 km / h.
Since the bus and the truck were moving in the same direction, the speed of approach is equal to the difference between their speeds, since the speed of the bus is 90 km / h, the speed of the truck will be:
90-30 = 70 km / h.