Here’s another way to think about the number line model for 2 – (-3): if we were adding 2 + (-3), we’d first move two units to t
he right. Then, we’d move three units to the left, because we move left when adding negative integers. But instead, we’re subtracting -3. Addition and subtraction are inverse operations, or opposite operations; they undo one another. So we move in the opposite direction, right, and end up with a sum of 5. As a result, the number line models for 2 – (-3) and 2 + 3 are identical. This shows that subtracting a negative integer is the same as adding a positive integer. Subtracting -9 from any number is the same as
A
subtracting 9 from that number.
B
subtracting 0 from that number.
C
adding 9 to that number.
D
adding -3 to that number.
