1/5 of charlies butterfly collection are red, of those that are not red 2/7 ths are monarch butterfy's. what is the least number of butterflys that could be in charlies collection?

Solution:

The number of butterflys is x

So

(2/7)(4/5)x = 8/35x should be integer

So

x=35

SO the least number of butterflys that could be in charlies collection is 35