Question 559438: 5 • (-3) – (-7)
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! 5 * (-3) – (-7) = -8
first multiply 5 * (-3) to get -15
then subtract (-7) from -15 to get -8
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when you multiply a positive number by a negative number, the result will always be negative.
that part was simple.
when you subtract, the rules are a little more complicated.
you can simplify them by converting the subtraction into an addition.
the rules for doing that are as follows:
subtracting a positive number is the same as adding a negative number.
subtracting a negative number is the same as adding a positive number.
the rules for addition come into play now.
if you are adding a positive number to a positive number, then you add both numbers together and make the sign positive.
if you are adding a negative number to a negative number, then you add both numbers together and make the sign negative.
if you are adding a negative number to a positive number, or a positive number to a negative number, then you subtract the smaller number from the larger number and make the sign of the result equal to the sign of the larger number
your particular situation is:
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your particular problem has resolved to:
- 15 - (-7)
this falls under the subtraction to addition conversion rule of:
subtracting a negative number is the same as adding a positive number.
your expression becomes:
- 15 + 7
this falls under the addition rule of adding a positive number to a negative number.
you subtract the smaller number from the larger number to get 15 - 7 = 8
you give the sign of the larger number to the result to get - 8.
that's why you got - 8 as the answer.
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