The correct answer is C = 200.
In this question, we have both the ratio and an absolute value. Thus, once we calculate the value of a unit of ratio we can easily find the rest of the values.
Since the ratio between the Roses and Lilies is 11:10, we can consider the 2,000 Lilies as 10 units of ratio and therefore: 2,000 Lilies/10 units = 200 Lilies per unit of ratio.
The difference between the number of Roses and the number of Lilies is one unit: 11-10 = 1, which equals 200.