5 weeks
There are 52 weeks per year and since the company closes for 2 weeks per year, that means that the company does business for 50 weeks each year. During that year, the company sold goods that cost $76,500. And the average inventory was $7,650 which is $7,650 / $76,500 = 0.10 = 10% of the goods sold for the entire year. So the average inventory could allow the company to work for 10% of the year. And 10% of 50 is 5. Therefore the company had 5 weeks of supply on average in inventory.