Can somebody me with this math problem?

Since the altitude OF sea level is 0, and the hiker in Death Valley is below sea level, the equation you would write would be :
-10 + 10. This is because the joker went from BELOW sea level, to the altitude OF sea level.
So, the answer should be A

The most logical situation would be A, the hiker starts at -10 feet the increases by 10 feet.

B. is close to A. but it wouldn't explain how the hiker stops at 0 feet. It'll just explain how he decreases by 10 feet going down to -20 feet

C. would be the same way w/ B. but now the elevation is above sea level and not below

D. however might confuse you into thinking that it is the correct answer because of the hiker starting at 0 feet. D. describes the hiker at 0 feet but then describes him increasing by 10 feet.

I hope this helps