Container C contains 8 brown marbles and 16 pink marbles. Container D contains 31 brown marbles and 9 pink marbles. How many pink marbles and brown marbles must be moved from Container D to put into Container C so that 50% of the marbles in Container A are brown and 75% of the marbles in Container D are brown?

	Container C		Container D
	Brown marbles	Pink marbles	Brown marbles	Pink marbles
Before	8	16	31	9
Change	+ ?	+ ?	- ?	- ?
After	1 u	1 u	3 p	1 p

50% = ⁵⁰₁₀₀ = 12

75% = ⁷⁵₁₀₀ = 34

Number of brown marbles = 8 + 31 = 39 

Number of pink marbles = 16 + 9 = 25 

1 u + 3 p = 39 --- (1)

1 u + 1 p = 25 ---(2)

(1) - (2)
(1 u + 3 p) - (1 u + 1 p) = 39 - 25
3 p - 1 p = 14
2 p = 14

1 p = 14 ÷ 2 = 7

From (2):
1 u + 1 p = 25
1 u + 1 x 7 = 25
1 u + 7 = 25

1 u = 25 - 7 = 18

Number of pink marbles to be moved from Container D to Container C
= 9 - 1 p
= 9 - 1 x 7
= 9 - 7
= 2

Number of brown marbles to be moved from Container D to Container C
= 1 u - 8
= 18 - 8
= 10

Total number of pink and brown marbles to be moved from Container D to Container C
= 2 + 10
= 12

Answer(s): 12