Scenario: Jake is a mountaineer who has climbed to an elevation of 1,200 feet above sea level. After resting at that height, he decides to rappel down a cliff to explore a cave below him. He lowers himself 1,500 feet down to enter the cave.
In this situation, the positive change is the action of Jake rappelling down 1,500 feet (a positive number). However, his final elevation after rappelling down that distance is -300 feet relative to sea level, which is represented as a negative number (1,200 feet - 1,500 feet = -300 feet).