the equation to find the slope between 2 points is
[tex]m=\frac{y2-y1}{x2-x1}[/tex]name the points
1=(11,9)
2=(12,9)
apply the formula
[tex]\begin{gathered} m=\frac{9-9}{12-11} \\ m=\frac{0}{1} \\ m=0 \end{gathered}[/tex]the slope between the points is 0.