For Jan's running shoes:Jan should return to the store where he bought the shoes and present the receipt as proof of purchase. He can request a replacement or a refund due to the defect. It is important to explain the issue clearly and check the store’s return policy.For Bob and Jerome's fish purchase:Jerome should remind Bob that he left his change with the vendor. They should go back to the vendor and politely ask for the change if it is still available. It is best to check their money before leaving the market to avoid missing any change.