Once upon a time, two ships were sailing merrily across the ocean when a storm came.
The storm blew the ships around, sending one to the bottom of the ocean and sending another to the top of a rocky formation.
The ship that got caught up on the rocks had an elevation of 273 feet.
The ship that sank went down 519 feet to the ocean floor.
Two kids who were on those ships survived and swam to shore. They had a measuring tape in their pocket and decided to find the difference in the two ships elevations.
They remembered their math class and came up with an equation. The equation was |273--519|. They did keep, change, change and got |273+519|. They added and found out that the ships were 792 feet apart!