There were yellow, purple and blue balls in a container. Sean put another 3 yellow balls and 2 blue balls in the container, then the ratio of the number of purple balls to the number of blue balls became 5 : 3. Then, he doubled the number of yellow balls and removed 16 blue balls. The ratio of the number of yellow balls to purple balls became 2 : 1. He counted and found that there were a total of 128 balls left in the container. Find the number of yellow balls that he had in the end.

	Yellow balls	Purple balls	Blue balls	Total
Before	5 u - 3	5 u	3 u - 2
Change 1	+ 3		+ 2
After 1	1x5 = 5 u	5 u	3 u
Change 2	+ 1x5 = 5 u		- 16
After 2	2x5 = 10 u	1x5 = 5 u	3 u - 16	128

The number of purple balls remains unchanged. Make the number of purple balls the same. LCM of 1 and 5 is 5.

Total number of balls in the end
= 10 u + 5 u + 3 u - 16
= 18 u - 16

18 u - 16 = 128
18 u = 128 + 16
18 u = 144

1 u = 144 ÷ 18 = 8

Number of yellow balls in the end
= 10 u 
= 10 x 8
= 80

Answer(s): 80