From 100 feet below sea level, Roger took off in his helicopter and ascended 100 feet. What is Roger's elevation now?

Question

please tell having little trouble

Answer 1

If Roger begins 100 ft below sea level and ascends 100 ft.  He would be at sea level.

 

Stating this mathematically

 

-100 + 100 = 0

 

where 0 = sea level.