Colleen has : 2 x 10 = 20 red roses and 2x5 = 10 yellow roses
Total roses = 20 + 10 = 30
Michelle has the same total roses in 3 vases:
30 roses/ 3 vases = 10 roses per vase.
If she has 6 red roses, then she would have 10-6 = 4 yellow roses per vase.
The answer is 4