Answer: The 2nd number line is correct
Explanation:
The first number line is incorrect because the -1, -2, -3 should be reversed to get -3, -2, -1. It's reversed because the negatives are a mirror image of the positive counterpart.
The second number line is correct. Each number shown is separated with a gap size of 20. This gap size stays the same throughout the number line.
The third number line is incorrect. The gap from -15 to -12 is 3 units, while the gap from -12 to -10 is 2 units. We see that the gap size isn't the same through the entire number line.
So to summarize: the gap size must be the same and the numbers must be written in the correct order.
