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

	Jack	Alexander	Benjamin
	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 Jack had at first is the repeated identity.
LCM of 3 and 20 = 60

The change in the number of stamps that Benjamin had is the repeated identity when Jack and Alexander gave to Benjamin.
LCM of 78 and 3 = 78

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

6 u = 18
1 u = 18 ÷ 6 = 3

Number of stamps that Jack and Alexander gave to Benjamin
= 52 u + 26 u
= 78 u
= 78 x 3
= 234

Answer(s): 234