Luis, Jeremy and David have some stickers. The ratios of their stickers are as follows:

Luis : (Luis + Jeremy + David) = 2 : 5
Jeremy : (Luis + David) = 1 : 3

David has 12 stickers more than Jeremy. In the end, David gives away all he has to Jeremy and Luis so that both Jeremy and Luis end up with the same number of stickers, how many stickers has Jeremy received from David?

Jeremy	David	Luis	Total
3x4		2x4	5x4
1x5	3x5		4x5
5 u	7 u	8 u	20 u

The total number of stickers is repeated.  Make the total number of stickers the same.  LCM of 5 and 4 is 20.

Number of stickers that David has more than Jeremy
= 7 u - 5 u
= 2 u

2 u = 12

1 u = 12 ÷ 2 = 6

	Jeremy	David	Luis
Before	5 u	7 u	8 u
Change	+ 5 u	- 7 u	+ 2 u
After	10 u	0 u	10 u

Number of stickers that Jeremy has received from David
= 10 u - 5 u 
= 5 u
= 5 x 6
= 30

Answer(s): 30