Container A contains 3 blue balls and 17 yellow balls. Container B contains 40 blue balls and 8 yellow balls. How many yellow balls and blue balls must be moved from Container B to put into Container A so that 50% of the balls in Container A are blue and 80% of the balls in Container B are blue?

	Container A		Container B
	Blue balls	Yellow balls	Blue balls	Yellow balls
Before	3	17	40	8
Change	+ ?	+ ?	- ?	- ?
After	1 u	1 u	4 p	1 p

50% = ⁵⁰₁₀₀ = 12

80% = ⁸⁰₁₀₀ = 45

Number of blue balls = 3 + 40 = 43 

Number of yellow balls = 17 + 8 = 25 

1 u + 4 p = 43 --- (1)

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

(1) - (2)
(1 u + 4 p) - (1 u + 1 p) = 43 - 25
4 p - 1 p = 18
3 p = 18

1 p = 18 ÷ 3 = 6

From (2):
1 u + 1 p = 25
1 u + 1 x 6 = 25
1 u + 6 = 25

1 u = 25 - 6 = 19

Number of yellow balls to be moved from Container B to Container A
= 8 - 1 p
= 8 - 1 x 6
= 8 - 6
= 2

Number of blue balls to be moved from Container B to Container A
= 1 u - 3
= 19 - 3
= 16

Total number of yellow and blue balls to be moved from Container B to Container A
= 2 + 16
= 18

Answer(s): 18