There are some white and pink balls in a box. If 3 white balls are removed from the box, the total number of balls left will be 9 times the number of white balls left. If 6 pink balls are removed from the box, the total number of balls left will be 6 times the number of white balls. How many balls are there in the box?

	Case 1		Case 2
	White balls	Pink balls	White balls	Pink balls
Before	1 u + 3	8 u	1 p	5 p + 6
Change	- 3			- 6
After	1 u	8 u	1 p	5 p

Number of pink balls in the end for Case 1
= 9 u - 1 u
= 8 u

Number of white balls in the end for Case 2
= 6 p - 1 p
= 5 p

The number of white balls at first is the same for Case 1 and Case 2.
The number of pink balls at first is also the same for Case 1 and Case 2.

1 u + 3 = 1 p --- (1)

8 u = 5 p + 6
8 u - 6 = 5 p --- (2)

Make p the same.

(1)_x5
5 u + 15 = 5 p --- (3)

(2) = (3)
8 u - 6 = 5 u + 15
8 u - 5 u = 15 + 6
3 u = 21

1 u = 21 ÷ 3 = 7

Number of balls in the box
= (1 u + 3) + 8 u
= 9 u + 3
= (9 x 7) + 3
= 63 + 3
= 66

Answer(s): 66