Question

120 pens are packed in 4 boxes with equal number of pens in Each box how many boxes would be needed to pack 15 dozen pens

Answer 1

Answer

6 boxes are used for packing 180 pens

Answer 2

Simple thing to do is follow unitary method 
144 pencils----1 box
1 pencil ----1/144box
100080 pencils ---100080/144=695 

so it needs 695 boxes to pack 100080 pencils