Question

A submarine is located 350 feet below the surface of the sea. It further sinks 85 feet. What is the submarine's current position?

Answer 1

Consider the heights above the sea level as positive numbers and the depths below the sea level as negative numbers

A submarine is located at $350$ feet below sea level, i.e., its postion is $-350$ ft.
It further sinks $85$ feet.
$\therefore$ The current location of the submarine below the sea level is
$[-350+(-85\left)\right]$ feet
$=(-350-85)$ feet
$=-435$ feet