During a telematch, each group of pupils was supposed to collect as many coloured balls as possible. Each colour represented a certain point as tabulated:

Colours	Points
Brown	4
Silver	6
Yellow	7

In each container, the number of brown balls was 80% more than the number of yellow balls and 90% less than the number of silver balls. Given that the total possible points if the group managed to collect all the balls were 1833 points, how many balls were not brown in colour?

Brown	Silver	Yellow
9x1		5x1
1x9	10x9
9 u	90 u	5 u

	Brown	Silver	Yellow	Total
Number	9 u	90 u	5u
Value	4	6	7
Total value	36 u	540 u	35 u	611 u

100% + 80% = 180%
180% = ¹⁸⁰₁₀₀ =⁹₅

100% - 90% = 10%
10% = ¹⁰₁₀₀ = ¹₁₀

Total number of points collected
= 36 u + 540 u + 35 u
= 611 u

611 u = 1833

1 u = 1833 ÷ 611 = 3

Number of balls not silver in colour
= 9 u + 5 u
= 14 u
= 14 x 3
= 42

Answer: 42