Respuesta :
D. x + (-x) = 0
That is the answer because if you are x feet above sea level, to get back to sea level, which equals zero (0), you need to go down the same amount you went up (x), so you need to go down x feet (-x).
That is the answer because if you are x feet above sea level, to get back to sea level, which equals zero (0), you need to go down the same amount you went up (x), so you need to go down x feet (-x).