To find the slope of two points you use the formula: [tex]\frac{y_{2} -y_{1} }{x_{2} -x_{1} }[/tex]
In this case we can assume that:
[tex]y_{2}[/tex] = -20
[tex]y_{1} =6[/tex]
[tex]x_{2} = - 9[/tex]
[tex]x_{1} = 1[/tex]
Plug the above into the equation I gave you at the start and solve:
[tex]\frac{-20 - 6}{-9 - 1}[/tex]
[tex]\frac{-26}{-10}[/tex]
Now reduce:
[tex]\frac{26}{10}[/tex]÷2
[tex]\frac{13}{5}[/tex]
^^^Slope for these two points
Hope this helped!