Answer:
y = -4
Explanation:
If you look at the y coordinate, you can see a common theme. They're all -4. The problem already states that the line is horizontal, meaning it doesn't move up or down on the y axis at all.
Just for good measure of learning, what do you think would happen if you had a line at x = -4? This would be a vertical line, and would not move along the x-axis.