Answer:
The journal entries to record the purchase and payment of the merchandise should be:
August 7, merchandise purchased, terms 1/10, n/30
Dr Merchandise inventory 9,750
  Cr Accounts payable 9,750
August 11, $1,500 worth of merchandise is returned
Dr Accounts payable 1,500
  Cr Merchandise inventory 1,500
August 26, invoice is paid at full amount since discount period expired
Dr Accounts payable 8,250
  Cr Cash 8,250