Respuesta :
Christy dove to the depth of 12 feet below the surface = -12 feet
(Below sea level means to be below zero, which are negative numbers)
Christy dove 12 feet back up to the surface= +12 feet
( When we come back up to the surface, the distance is taken always positive)
Therefore, we have to find the overall change,
Overall change = -12 feet + 12 feet
= -12 feet + 12 feet
= 0 ft.
Therefore, overall change is 0 ft.