Christopher bought 50% more stamps than Elizabeth. Ella bought 35% fewer stamps than Christopher. Christopher and Elizabeth gave Ella some stamps in the ratio 2 : 1. As a result, Ella had twice as much stamps as before. Given that Christopher had 18 less stamps than Elizabeth in the end, how much stamps did Christopher and Elizabeth give to Ella?

	Christopher	Elizabeth	Ella
	3x20	2x20
	20x3		13x3
Before	60 u	40 u	39 u
Change			+ (2 x 39 u) = + 78 u
	- 2x26 = - 52 u	- 1x26 = - 26 u	+ 3x26 =  + 78 u
After	8 u	14 u	117 u

100% + 50% = 150%
150% = ¹⁵⁰₁₀₀ = ³₂

100% - 35% = 65%
65% = ⁶⁵₁₀₀ = ¹³₂₀

The number of stamps that Christopher had at first is the repeated identity.
LCM of 3 and 20 = 60

The change in the number of stamps that Ella had is the repeated identity when Christopher and Elizabeth gave to Ella.
LCM of 78 and 3 = 78

Number of stamps that Christopher had less than Elizabeth in the end
= 14 u - 8 u
= 6 u

6 u = 18
1 u = 18 ÷ 6 = 3

Number of stamps that Christopher and Elizabeth gave to Ella
= 52 u + 26 u
= 78 u
= 78 x 3
= 234

Answer(s): 234