Currently have 12 bottles of water on your shelf and want to keep an minimum level of 6 bottles at all times. you average sales of 2 bottles per day. what is the minimum number you would order for enough bottles for 7 days

If you wish to have 6 or more bottles on the shelf at any given time, and you sell 2 a day, and you are open 7 days a week, then you'd want to start each week with at least 6 + (2·7)= 20 bottles. You have 12, so you'd need to order 8 more that for that next week.

Hope this helps.

Yes you are correct