Add all of the numbers 50+30+100=180 and you have to find 180s multiples which are 1,2,3,4,5,6,9,10,12,15,18,20,30,36,45,60,90,180. So you can do and of those numbers and just divide them by 180 to find the number of items that would be inside the box. For example, 180 divided by 3 boxes would be 60 items in each box.