Adding/Subtracting Negative Numbers

1. I would introduce the number line and talk about what direction you move if you are adding (right) and what direction you move if you're subtracting (left).
2. I would then work on things like 2 + 6 and 2 - 6 and use the number line to emphasize point 1 above.
3. Then I would ask "what if I ADD a negative number like 2 + (-6)?". In this case, you're talking about adding (going to the right), but you're adding a NEGATIVE so you actually end up going to the left. So 2 + (-6) is a lot like 2 - 6. Hopefully you can make a connection to when you did 2 - 6 above.
4. Do the same with a negative. So something like 2 - (-6). In this case, we are subtracting so we're going to the left. But we're subtracting a negative so we go back to the right. so 2 - (-6) is a lot like 2 + 6. Hopefully you can make a connection to when you did 2 + 6 in point 2 above.
5. In terms of steps, whenever your student sees a problem like -2 - 5, that they should break it into three parts: the first number, the operation (+ or -) and the second number. So for -2 - 5, I would first start by saying that's (-2) - (+5). Make it explicit. Then you can say, ok we're starting at -2 and we're SUBTRACTING (moving to the left) +5. Since the 5 is positive, we just move to the left.

Another example:
-5 - -6: