Answer:
6 sacks
Explanation:
Mr. Drucker tries to always hold 15 sacks on his shelf to keep his inventory in stock. He currently has 9 sacks. Since 15 - 9 = 6, he needs to order 6 sacks.
This problem has many extraneous values which are good information about Mr. Drucker's buisness but do not pertain to how much he needs to order to maintain 15 sacks on his shelf.