In order for us to solve this problem, we need to make the units uniform first to make it easier. 1 yard is equivalent to 3 feet. Therefore, one bag can cover 1 yard^2. Since the bed measures 6 and 1/2 feet by 11 feet, the area of this bed is 71.5ft^2. The bag of mulch can cover an area of 9ft^2. Therefore, if we divide 71.5 by 9, then we get 7.9 or 8. So Heather would need 8 bags of mulch to cover the flower bed. Hope this answer helps.