Without the line

No number line near you? Four short questions give the answer.

A number below 0 points left. A number above 0 points right.

Rule — four short questions, in order:

1. Is it a take-away? Rewrite it as an add.
2. Do both numbers point the same way? Add the sizes. Keep that side.
3. Different ways? Take the smaller size from the bigger. Keep the bigger move's side.
4. Same size, opposite ways? The answer is 0.

Try (−6) − (−9) = (−6) + 9. The sizes are 6 and 9 steps. So 9 − 6 = 3. The bigger move points right. So the answer is 3.

Tap the answer in the lab. Then check it on the line.

Try the lab to finish this lesson.