There were green, yellow and silver balls in a bottle. Sean put another 6 green balls and 7 silver balls in the bottle, then the ratio of the number of yellow balls to the number of silver balls became 5 : 2. Then, he doubled the number of green balls and removed 16 silver balls. The ratio of the number of green balls to yellow balls became 2 : 1. He counted and found that there were a total of 35 balls left in the bottle. Find the number of green balls that he had at first.

	Green balls	Yellow balls	Silver balls	Total
Before	5 u - 6	5 u	2 u - 7
Change 1	+ 6		+ 7
After 1	1x5 = 5 u	5 u	2 u
Change 2	+ 1x5 = 5 u		- 16
After 2	2x5 = 10 u	1x5 = 5 u	2 u - 16	35

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

Total number of balls in the end
= 10 u + 5 u + 2 u - 16
= 17 u - 16

17 u - 16 = 35
17 u = 35 + 16
17 u = 51

1 u = 51 ÷ 17 = 3

Number of green balls at first
= 5 u - 6
= 5 x 3 - 6
= 15 - 6
= 9

Answer(s): 9