Final answer:
The number that represents an elevation of 735 feet below sea level is -735 feet.
Step-by-step explanation:
The number that represents an elevation of 735 feet below sea level is -735 feet.
Elevations below sea level are typically represented with negative numbers. In this case, since the elevation is below sea level, the number is negative.
For example, if sea level is represented by 0, then an elevation of 735 feet below sea level would be represented by -735.