Answer:
0
Step-by-step explanation:
First, you have to plug it into the formula to find the slope.
[tex]\frac{rise}{run}[/tex] =[tex]\frac{y2-y1}{x2-x1}[/tex]
[tex]\frac{8-8}{-5-10} =\frac{0}{-15}[/tex]
Since 0 divided by anything is 0, that gives us 0 as a slope and it would be horizontal.