Answer:
-1,487.9
Step-by-step explanation:
Subtract 215.5 from -1,275.5.
-1,491
then add 125.5 to -1,491.
-1,365.5
finally, subtract 122.4 from -1,365.5.
-1,487.9
Essentially, you are starting at 1,275.5 feet below sea level, which makes it negative.