David and Paul shared some stamps in the ratio of 5 : 7. After both each gave away 143 stamps to their brother, the ratio of the number of stamps David had to the total number of stamps left was 1 : 5. How many stamps did the two boys have in the end?

	David	Paul	Difference
Before	5x3 = 15 u	7x3 = 21 u	2x3 = 6 u
Change	- 143	- 143
After	1x2 = 2 u	4x2 = 8 u	3x2 = 6 u

Number of stamps that David and Paul each gave to their brother is the same.

The difference in the number of stamps at first and in the end between David and Paul remains unchanged.  Make the difference in the number of stamps the same.  LCM of 2 and 3 is 6.

Number of stamps that David gave to their brother
= 15 u - 2 u
= 13 u

13 u = 143

1 u = 143 ÷ 13 = 11

Number of stamps that the two boys had in the end
= 2 u + 8 u
= 10 u
= 10 x 11
= 110

Answer(s): 110