Answer:
-60+30=(-30)
Step-by-step explanation: The whale was swimming 60 feet BELOW sea level. That's negative. Then it swims up 30 feet, that's positive. Add to get -30, since -60 is the greater number although not in value. you get -30, so move the dot up , and the whale is now 30 feet below the surface.
Please let me know if this helped.