Firstly, we need to know the number of boxes they both filled per hour.
From the question, we are told that 126 boxes were filled in six hours; thus in an hour, the number of boxes filled will be 126/26 = 21 boxes
Now in an hour, Nicholas filled 9 boxes; the number of boxes that will be filled is clearly the remainder of the 21 boxes.
The number of boxes filled by Jack is thus; 21 - 9 = 12 boxes
Jack fills 12 boxes in an hour
