There were white, grey and purple balls in a container. Sean put another 2 white balls and 3 purple balls in the container, then the ratio of the number of grey balls to the number of purple balls became 4 : 3. Then, he doubled the number of white balls and removed 11 purple balls. The ratio of the number of white balls to grey balls became 2 : 1. He counted and found that there were a total of 79 balls left in the container. Find the number of white balls that he had in the end.

	White balls	Grey balls	Purple balls	Total
Before	4 u - 2	4 u	3 u - 3
Change 1	+ 2		+ 3
After 1	1x4 = 4 u	4 u	3 u
Change 2	+ 1x4 = 4 u		- 11
After 2	2x4 = 8 u	1x4 = 4 u	3 u - 11	79

The number of grey balls remains unchanged. Make the number of grey balls the same. LCM of 1 and 4 is 4.

Total number of balls in the end
= 8 u + 4 u + 3 u - 11
= 15 u - 11

15 u - 11 = 79
15 u = 79 + 11
15 u = 90

1 u = 90 ÷ 15 = 6

Number of white balls in the end
= 8 u 
= 8 x 6
= 48

Answer(s): 48