Question

The lowest point in a particular country is negative 548−548 feet at a particular lake in a particular place. if you are standing at a point 660660 feet above the​ lake, what is your​ elevation?

Answer 1

The question is a bit ambiguous: when you want to compute the elevation of something, you have to define a zero-elevation point, so that you can compute the elevation of anything with respect to that zero-elevation point. Given the coordinate $y_0$ of the zero-elevation point, the altitude of every other point with coordinate $y_1$ is given by $y_1 - y_0$

So, assuming that the zero-elevation point is the bottom of the lake, and thus $y_0 = -548$, your altitude at $y_1 = 660$ is

$y_1 - y_0 = 660 - (-548) = 660+548 = 1208$