Answer:
0
Explanation:
The slope is the variation of the inclination of a straight line.
It's measured by calculating the variation of the y values (rise) over the variation of the x values (run). Let's take 2 points over that line: (0,-3) and (2,-3).
We see the variation of y values is 0: -3 - -3 = 0
The variation of x values is 2: 2 - 0 = 2
So, the slope is 0/2, so 0.
Horizontal lines don't have a slope because they don't vary in the y values... just like a flat land isn't a hill, there's no slope.