Answer:
The elevation closest to the sea level is –42ft and the elevation farthest from the sea level is –8ft.
Step-by-step explanation:
Let's assume the elevation above the sea level is on a number line, then we have to arrange the given number from lowest to highest. These are the numbers in ascending order.
–42ft, –20ft, –18ft, –8ft.
From here we see that, the elevation closest to the sea level is –42ft and the elevation farthest from the sea level is –8ft.