There are 5 yellow roses in each of Michelle's vases.
Colise
2 vases x 10 red roses = 20 total red roses
2 vases x 5 yellow roses = 10 total yellow roses
20 red roses + 10 yellow roses = 30 total roses
Michelle
30 total roses / 6 red roses in each vase = 5 yellow roses in each vase