The simple rule is to change subtraction problems into addition
problems. I mean it. To subtract a number you just add its
opposite. Change all the subtraction symbols to
addition symbols. Then change the sign of the number that
followed the original subtraction symbol.
Here's an example:
7 - (-4) = ?
If we change this to an addition problem, we now have:
7 + 4 = 11
We changed the subtraction symbol to addition and we changed
the negative four to a positive four. Then use the rules for addition
found on page one.
-8 - (9) = ? becomes -8 + (-9) = -17
-10 - (-7) = ? becomes -10 + 7 = -3
98 - 64 = ? becomes 98 + (-64) = 34
Link to Addition of signed numbers
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