Assume perpetual inventory system:
March 7 purchased good from James Co on account $13,500, terms 4/10, n/30.
March 13 returned merchandise to James co that was previously purchased on account $1350
March 18 paid the amount due to James Co

Mar 7
Debit Inventroy for the amount
Credit Accounts Payable for the amount

Mar 13
Debit Accounts Payable for the amount of the return
Credit Inventory for the amount returned.

Mar 18
Debit Accounts Payable for the Balance of the account
Credit Cash for the balance

Note: Discount is lost because you did not pay within the 10 day discount period.