Answer:
The new position of submarine is 550 feet below the sea level.
Given:
A submarine is located at 800 feet below sea level (i.e) if x is considered as the sea level, then it is located at x - 800. The submarine ascends 250 feet, (i.e) its new position is increased by 250 feet from its previous position, then its new position becomes 800 - 250 = 550 feet. Hence the new position of submarine is located at 550 feet below sea level, x.