11. simplify each expression.
a. 502+(-12.3)
b. -50.2+(-12.3)
c. -50.4+ 12.3
12. at the beginning of the day, the stock market
goes up 30 points. at the end of the day, the
stock market goes down 120 points. what is
the total change in the stock market from the
beginning of the day to the end of the day?
13. a dolphin is swimming 18 feet below the surface
of the ocean. there is a coast guard helicopter
75.5 feet above the surface of the water that is
directly above the dolphin. what is the distance
between the dolphin and the helicopter?