Final answer:
After returning $3,000 worth of merchandise, the adjusted accounts payable for the Preston Company will be $37,000, reflecting the actual amount owed for the purchases made.
Step-by-step explanation:
The Preston Company recorded purchases of $40,000 at net amounts. When $3,000 of merchandise was returned, the accounts payable should be adjusted to reflect the net amount after the return. Initially, the purchase was recorded at $40,000; after returning $3,000 worth of merchandise, the correct accounts payable will be the initial amount less the return amount. Therefore, the adjusted accounts payable will be $40,000 - $3,000 = $37,000, reflecting the cost of merchandise that the company still owes to its suppliers.