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You are correct. By changing the sign of the number being subtracted, and then adding instead of subtracting that number, you get
( − 7) − ( + 3) = ( − 7) + ( − 3) = ( − 10)
by the rule for adding numbers with like signs.
We have been quite formal in writing 3 as ( + 3), etc., in the last few pages. We are going to drop this now and rely on you to remember that a number with no sign shown is regarded as positive. Thus, 7 − ( − 3) means ( + 7) − ( − 3), and − 8 − 5 means ( − 8) − ( + 5). The - sign between the 8 and the 5 in “ − 8 − 5” is not the sign of the 5; it is the instruction to us to subtract the number following the sign. Whenever the number to be subtracted (the subtrahend) is a negative number, it is written in parentheses.
