What you must keep in mind is that there are 4 jeans in total, which represents 100% When she bought two jeans, we have the following information: If both of them are blue: 50% of their jeans is blue now, that is: x = (50/100) * 4 = 2 2 jeans are blue. This means that she did NOT have 2 blue jeans before. Thus: If they are not blue: We have 4 jeans that are not blue. Then, 0% of her jeans is blue now answer: 0% percentage of her jeans is blue now