Do you need help with anything?
Melody and CPhil answer the same question at this link: https://web2.0calc.com/questions/word-problem_21
Sorry, I just logged in and I saw this question.
So if you start hiking 550 meters below sea level, then our elevation would be -550 meters above sea. (I know that wouldn't make sense.) We have:
So, now we are 505 meters below sea level.
Hope this helps!