As the barge can safely haul no more than 400 tons across the river, and the barge itself has an empty weight of 24 tons, it has an available capacity of 376 tons (400-24). So, as every railroad car weighs 4 tons, in order to know how many railroad cars the barge can haul we have to divide the available capacity by the weight of each railroad car.
According to it, we have to divide 376 by 4 (376 / 4), which gives us a result of 94, which is the maximum number of railroad cars that the barge can haul.
If the plant grows 7cm every 7 days then you simply have to add 7 for each time it goes up 4. For example from 4-8 it went up 4 therefore you add 7. 7+7= 14. Then you repeat the process for all other numbers
