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Adding and subtracting negative numbers

8 – ( – 12) = ?

Adding and subtracting negative numbers

If a number has no sign it means that it is a positive number (positive number are higher than 0). We can write it with a plus sign, e.g. 5=+5. We add and subtract, as we normally do. The sum of two positives numbers is always positive (higher than zero).

Subtraction of two positive numbers can take us beyond zero in some cases: 3−10=(−7) To add and subtract with negative numbers, at first add positive signs to positive numbers, e.g. 20−5=20−+5

For each combination of two signs follow these rules:

RuleExample

Two like signs (++ or −−) become a positive sign.

5+(+3)=5+3=8
−5+(+3)=−5+3=−2
2−(−3)=2+3=5
−4−(−3)=−4+3=−1

Two unlike signs (+− or −+) become a negative sign.

4+(−3)=4−3=1
−8+(−4)=−8−4=−12
1−(+3)=1−3=−2
−5−(+4)=−9

   
   

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