Using addition, the submarine is 38 feet below sea level.
What is addition?
The addition is "taking two or more numbers and adding them together, or it is the total sum of two or more numbers".
According to the question,
A submarine was at 30 feet below sea level. The submarine sinks 8 more feet. In order to find, number of feet below sea level the submarine only if we add 30 feet and 8 feet.
= 30 + 8 = 38 feet.
Hence, using addition the submarine is 38 feet below sea level.
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