Container W contains 2 yellow beads and 4 black beads. Container X contains 23 yellow beads and 9 black beads. How many black beads and yellow beads must be transferred from Container X to put into Container W so that 50% of the beads in Container A are yellow and 80% of the beads in Container X are yellow?

	Container W		Container X
	Yellow beads	Black beads	Yellow beads	Black beads
Before	2	4	23	9
Change	+ ?	+ ?	- ?	- ?
After	1 u	1 u	4 p	1 p

50% = ⁵⁰₁₀₀ = 12

80% = ⁸⁰₁₀₀ = 45

Number of yellow beads = 2 + 23 = 25 

Number of black beads = 4 + 9 = 13 

1 u + 4 p = 25 --- (1)

1 u + 1 p = 13 ---(2)

(1) - (2)
(1 u + 4 p) - (1 u + 1 p) = 25 - 13
4 p - 1 p = 12
3 p = 12

1 p = 12 ÷ 3 = 4

From (2):
1 u + 1 p = 13
1 u + 1 x 4 = 13
1 u + 4 = 13

1 u = 13 - 4 = 9

Number of black beads to be transferred from Container X to Container W
= 9 - 1 p
= 9 - 1 x 4
= 9 - 4
= 5

Number of yellow beads to be transferred from Container X to Container W
= 1 u - 2
= 9 - 2
= 7

Total number of black and yellow beads to be transferred from Container X to Container W
= 5 + 7
= 12

Answer(s): 12