The key to knowing whether to add or subtract is to know what kind of numbers you are working with; positive or negative numbers. It is up to us to determine what we’re working with, and practicing multiple types of problems is important in becoming familiar with the different kinds of numbers. This video will review what we have covered on addition and subtraction with positive and negative numbers:

Video Source (08:49 mins) | Transcript

Additional Resources

• Khan Academy: Adding & Subtracting Negative Numbers (04:06 mins, Transcript)

Practice Problems

1. \(4 - 9 = ?\) (
   Solution

   x

   Solution: \(-5\)
   Details:
   Subtraction can be rewritten as the addition of the opposite.
   
   We can change this problem to addition by turning \(-9\) into \(+(-9)\).
   
   \(4 - 9 = -5\) is the same as \(4 + ( - 9) = -5\)
   )
2. \(7 + (-9) = ?\) (
   Video Solution

   x

   Solution: \(-2\)
   Details:
   

   
   (Video Source | Transcript)
   )
3. \(10 - (-7) = ?\) (
   Solution

   x

   Solution: \(17\)
   Details:
   Subtraction can be rewritten as the addition of a negative number.
   
   To solve this problem, we can turn the subtraction to addition by adding the opposite of \(- 7\) which is \(7\).
   
   Our problem \(10 - ( -7 )\) becomes: \(10 + ( 7 ) = 17\)
   )
4. \(-8 + 4 = ?\) (
   Video Solution

   x

   Solution: \(-4\)
   Details:
   

   
   (Video Source | Transcript)
   )
5. \(-4 + (-4) = ?\) (
   Solution

   x

   Solution:
   \(-8\)
   )
6. \(-8 - (-4) = ?\) (
   Solution

   x

   Solution:
   \(-4\)
   )

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