Answer:
0 or a undefined slope.
Explanation:
The equation to find the slope of a lines requires two points, which you are given in the question. I'm not sure how to use the math symbols on this thing, so just research for the equation or use y2-y2/x2-x1. It looks really weird in that format, but basically subtract the two y-values, it doesn't matter which one is first, and then subtract the two x-values, it also doesn't matter which one is first. Put the difference of the y-values on the numerator and the different of the x-values on the denominator. This will result in a slope of 0 or a undefined slope.
Here is the math work:
Subtracting the y-values
-9-(-7) = -2
Subtracting the x-values
-9-(-9) = 0
Putting It "Together"