Final answer:
Jem showed Scout his box of treasures, including a football medal to cheer her up after her disagreement with Aunt Alexandra.
Step-by-step explanation:
Jem Finch showed his sister, Scout, something he was very proud of after her disagreement with Aunt Alexandra in To Kill a Mockingbird. Jem presented Scout with a box containing his collection of things he had found and treasured, which helped to make her feel better. Among the items was a medal he had won in football, which he considered his biggest accomplishment and source of pride at that time.