Emily, Penelope and Sabrina had a total of 69 stamps. The ratio of Penelope's stamps to Sabrina's stamps was at first 4 : 9. After Emily and Penelope each gave half of their stamps away, the 3 children had 48 stamps left. How many stamps did Emily and Sabrina have at first?

	Emily	Penelope	Sabrina	Total
Before	2 p	4 u	9 u	69
Change	- 1 p	- 2 u		- 21
After	1 p	2 u	9 u	48

Number of stamps that Emily and Penelope gave away
= 69 - 48
= 21

1 p + 2 u = 21
1 p = 21 - 2 u --- (1)

1 p + 2 u + 9 u = 48 
1 p + 11 u = 48
1 p = 48 - 11 u --- (2)

(1) = (2) 
21 - 2 u = 48 - 11 u 
11 u - 2 u = 48 - 21
9 u = 27

1 u = 27 ÷ 9 = 3

From (1)
1 p = 21 - 2 u
1 p = 21 - 2 x 3

1 p = 21 - 6 = 15

Number of stamps that Emily and Sabrina had at first
= 2 p + 9 u
= 2 x 15 + 9 x 3
= 30 + 27
= 57

Answer(s): 57