Answer: Line 3
Explanation:
On the third line is where the student went from -12-3 to -9. This is not correct. Instead, it should be -12-3 turning into -15.
Think of it like being 12 feet under water (the number -12) and then moving 3 more feet deeper under water. You'll move down 3 to get to -15 to represent being 15 feet under water. Use a vertical number line if needed.
You can also compute -12-3 like 12+3 = 15, then just make everything negative. So -12-3 = -15
