To calculate the slope m of the line that passes through two points
[tex]\begin{gathered} A(x_1,y_1) \\ B(x_2,y_2) \end{gathered}[/tex]Using the formula
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]Let's use this with the points
[tex]\begin{gathered} A(-20,-4) \\ B(-12,-10) \end{gathered}[/tex]This way,
[tex]\begin{gathered} m=\frac{-10-(-4)}{-12-(-20)}\rightarrow m=\frac{-10+4}{-12+20}\rightarrow m=\frac{-6}{8} \\ \rightarrow m=-\frac{3}{4} \end{gathered}[/tex]