The answer is 22.17 km/hr. The total distance would be the sum of the first 73 kilometers and the second distance 60 kilometers, and the time the train took to cover that distance would be the sum of the first 3 hours and the second 3 hours. Since the average speed of the train is the total distance it traveled divided by the elapsed time to cover that distance, we have
average speed = total distance/elapsed time
= (73km + 60km) / (3hr + 3hr)
= 133km / 6hr
= 22.17 km/hr