The 81 balls need to be split into some number of boxes. To figure out how many boxes, we can divide the 81 balls by the 7 ball capacity of a single box.
81/7 = 11.571
This means that we will need 11 full boxes, but there will be a remainder of balls which did not fit. Since we can't have a fraction of a box, we need to round up to 12 boxes to hold all 81 balls.
