- Subtraction can be thought of as the inverse operation of addition, OR as addition itself, if you look at it as adding a negative number.
- The number line allows us to interpret subtraction (or addition of a negative) geometrically; we can view it as a movement to the left on the number line with a distance equal to the number being subtracted.
- Lastly, the value of any expression a - b (where a and b are real numbers) is determined by the relative sizes of the numbers. If a > b, then a - b > 0 (a positive result). If b > a, then a - b < 0 (a negative result.