Box Q contains 3 yellow balls and 9 brown balls. Box R contains 29 yellow balls and 9 brown balls. How many brown balls and yellow balls must be moved from Box R to put into Box Q so that 50% of the balls in Box A are yellow and 75% of the balls in Box R are yellow?

	Box Q		Box R
	Yellow balls	Brown balls	Yellow balls	Brown balls
Before	3	9	29	9
Change	+ ?	+ ?	- ?	- ?
After	1 u	1 u	3 p	1 p

50% = ⁵⁰₁₀₀ = 12

75% = ⁷⁵₁₀₀ = 34

Number of yellow balls = 3 + 29 = 32 

Number of brown balls = 9 + 9 = 18 

1 u + 3 p = 32 --- (1)

1 u + 1 p = 18 ---(2)

(1) - (2)
(1 u + 3 p) - (1 u + 1 p) = 32 - 18
3 p - 1 p = 14
2 p = 14

1 p = 14 ÷ 2 = 7

From (2):
1 u + 1 p = 18
1 u + 1 x 7 = 18
1 u + 7 = 18

1 u = 18 - 7 = 11

Number of brown balls to be moved from Box R to Box Q
= 9 - 1 p
= 9 - 1 x 7
= 9 - 7
= 2

Number of yellow balls to be moved from Box R to Box Q
= 1 u - 3
= 11 - 3
= 8

Total number of brown and yellow balls to be moved from Box R to Box Q
= 2 + 8
= 10

Answer(s): 10