Answers

2014-07-13T17:59:32+08:00
When negative is subtracted by positive, add it

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2014-07-13T18:34:29+08:00
Change the sign of the subtrahend then change the operation sign
then proceed to the rules of addition
Ex. -6 - 6             9 - (-6)
      -6 + (-6)         9 + 6 
      = -12             = 15 
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