Container G contains 17 yellow marbles and 9 black marbles. Container H contains 50 yellow marbles and 22 black marbles. How many black marbles and yellow marbles must be removed from Container H to put into Container G so that 50% of the marbles in Container A are yellow and 80% of the marbles in Container H are yellow?

	Container G		Container H
	Yellow marbles	Black marbles	Yellow marbles	Black marbles
Before	17	9	50	22
Change	+ ?	+ ?	- ?	- ?
After	1 u	1 u	4 p	1 p

50% = ⁵⁰₁₀₀ = 12

80% = ⁸⁰₁₀₀ = 45

Number of yellow marbles = 17 + 50 = 67 

Number of black marbles = 9 + 22 = 31 

1 u + 4 p = 67 --- (1)

1 u + 1 p = 31 ---(2)

(1) - (2)
(1 u + 4 p) - (1 u + 1 p) = 67 - 31
4 p - 1 p = 36
3 p = 36

1 p = 36 ÷ 3 = 12

From (2):
1 u + 1 p = 31
1 u + 1 x 12 = 31
1 u + 12 = 31

1 u = 31 - 12 = 19

Number of black marbles to be removed from Container H to Container G
= 22 - 1 p
= 22 - 1 x 12
= 22 - 12
= 10

Number of yellow marbles to be removed from Container H to Container G
= 1 u - 17
= 19 - 17
= 2

Total number of black and yellow marbles to be removed from Container H to Container G
= 10 + 2
= 12

Answer(s): 12