Answer:
C
explanation:
The answer is C because when adding negatives and positives your basically subtracting. I know that its -55 because it says in the word problem your swimming 55 depths below, below helps me determine if its going to be negative or positive. I got 20 because since it says 20 feet up, up helps me determine if the swimmer is going up or down.
Extra Help:
When doing these problems make sure to look for words like below, down , and withdraw, these are a hint its going to be negative.
Also look for words like above, up, and deposit these can mean positive.
When adding numbers with the same sign it has to be that sign and its just plain old adding. When add numbers with the opposite sign its going to be the sign with the bigger number and its going to contain subtracting.
Example:
50 + 51 = 101
50 + -51 = 1
-72 + 30 = -42
