* Marianas Trench Depth: The deepest point of the Marianas Trench is the Challenger Deep, approximately 10,902 meters (35,768 feet) below sea level.

* Mount Everest Height: The height of Mount Everest is approximately 8,848 meters (29,029 feet) above sea level.

Calculation:

* Total Difference: 10,902 meters (Trench depth) + 8,848 meters (Everest height) = 19,750 meters

Therefore, the approximate difference in elevation from the bottom of the Marianas Trench to the top of Mount Everest is about 19,750 meters (64,803 feet).