Question 1000906
Since 1/3 are black and 2/9 are white, that accounts for
1/3 + 2/9 = 3/9 + 2/9 = 5/9 of all the balls.
That means the rest of the balls are 4/9 of them.
The six that are yellow and two which are red, are those 4/9.
If eight balls represent 4/9, then there are 18 balls total, 
4/9 of 18 is 8.
Thus there are 6 black (1/3 of 18) and 4 white (2/9 of 18) balls.