We are given the fractions representing the number of discs in the bag. When comparing fractions, we should first find a common denomenator for them. The smallest common denomenator for 6 and 4 is 12 (43=12; 62=12). When converting fractions, remember the rule "Whatever we do to the bottom, we must do to the top." This means that 1/6 = 2/12 and 1/4 = 3/12. Now we add these two fractions together to get 5/12. This means that out of 12 discs in the bag, 5 of them are red and blue. This would allow us to work out the white discs to be 12-5=7 discs.