So each of Colise vases have 15 roses in them so she has a total of 30 roses 20 red and 10 yellow. Michelle also has 30 roses but he has three vases, each with 6 red roses, 6 x 3 is 18 and 30 - 18 is 12, 12/3 is 4 so Michelle would have 4 yellow roses in each of her vases.