Zoe had 50% more marbles than Jackson. Bryan had 20% fewer marbles than Zoe. Zoe and Jackson gave Bryan some marbles in the ratio of 4 : 5. As a result, Bryan had 25% more marbles than before. Given that Bryan had 140 more marbles than Jackson in the end, how many marbles did Zoe give to Bryan?

Zoe	Jackson	Bryan
3x5	2x5
5x3		4x3
15	10	12

100% + 50% = 150%
150% = ¹⁵⁰₁₀₀ = ³₂

Zoe : Jackson = 3 : 2

100% - 20% = 80%
80% = ⁸⁰₁₀₀ = ⁴₅

Zoe : Bryan = 5 : 4

The number of marbles that Zoe had at first is repeated. Make the number of marbles that Zoe had at first the same.  LCM of 3 and 5 is 15.

	Zoe	Jackson	Bryan
Before	15x3 =  45 u	10x3 = 30 u	12x3 = 36 u
Change			+ 3x3 = + 9 u
Comparing the changes in the number of marbles	- 4x1 = - 4 u	- 5x1 = - 5 u	+ 9x1 = + 9 u
After	41 u	25 u	15x3 = 45 u

25% x 12 
= ²⁵₁₀₀ x 12 
= 3 

The total number of marbles that Zoe and Jackson gave to Bryan is repeated.  Make the total number of marbles that Zoe and Jackson gave to Bryan the same.  LCM of 9 and 3 is 9.

Number of marbles that Bryan had more than Jackson 
= 45 u - 25 u
= 20 u

20 u = 140

1 u = 140 ÷ 20 = 7

Number of marbles that Zoe gave to Bryan
= 4 u
= 4 x 7
= 28

Answer(s): 28