A freight train fills its gas cars at the refinery to transport it. The weight of the train with its full load is 123 tons.
At the first stop, you unload half of the gasoline you were transporting and now the weight of the train with the rest of the load is 98 tons.
Finally, at the last station, empty the rest of the load he carried.
How much does the train weigh now?
If half of the gasoline has been unloaded and 123 - 98 = 25 tons are lost in the process, the initial total load is exactly double, that is 50 tons and the train therefore weighs 123 - 50 = 98 - 25 = 73 tons.