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

Colours	Points
Black	3
Silver	6
Grey	8

In each container, the number of black marbles was 20% more than the number of grey marbles and 70% less than the number of silver marbles. Given that the total possible points if the group managed to collect all the marbles were 1068 points, how many marbles were not black in colour?

Black	Silver	Grey
6x1		5x1
3x2	10x2
6 u	20 u	5 u

	Black	Silver	Grey	Total
Number	6 u	20 u	5u
Value	3	6	8
Total value	18 u	120 u	40 u	178 u

100% + 20% = 120%
120% = ¹²⁰₁₀₀ =⁶₅

100% - 70% = 30%
30% = ³⁰₁₀₀ = ³₁₀

Total number of points collected
= 18 u + 120 u + 40 u
= 178 u

178 u = 1068

1 u = 1068 ÷ 178 = 6

Number of marbles not black in colour
= 20 u + 5 u
= 25 u
= 25 x 6
= 150

Answer: 150