Directed numbers 文字題

1. An elevator starts at the twelfth floor and then goes down six floors. At which floor does the elevator finally stop?

Answer: The elevator finally stops at:
(+12)-(+6)
=+12-6
=6/F

2. A diver first dives from sea-level to a position 10 m below sea-level, the she further dives to another position 50 m below sea-level. How deep has she dived in her second part of diving?

Answer: She has dived:
(-10)-(-50)
=-10+50
=40 m

Hope can help you la!

a submarine moved up 120m from 250 m below the sea-level,then decending by 70 m, Ues a directed number to reprsent the location of the submarine.