Answer
$20,602$ feet
Work Step by Step
Finding the difference in elevation means that the higher elevation must be subtracted by the lower elevation.
The higher elevation is $20320$ feet above sea level, and the lower elevation is $282$ feet below sea level. This second value can be expressed as $-282$ in the calculation, since the numbers are relative to sea level.
Thus:
$20320 - (-282) = 20602$ feet
