If he descends 60.5 feet from the top of the reef, then the elevation to the top of the reef is 60.5 feet
This problem can be solved simply by subtracting 60.5 from -20.5 because the diver started at -20.5 ft and then descended another 60.5 ft. Since, we are subtracting a number from a negative number, that means that the answer will too be negative.
-20.5-60.5=-81
The elevation of the top of the coral reef is -81 ft.
Hope this helps!
