The formula to find the slope of a line is:
[tex]\begin{gathered} m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}} \\ \text{ Where m is the slope and} \\ (x_1,y_1)\text{ and }(x_2,y_2)\text{ are two points through which the line passes} \end{gathered}[/tex]So, in this case, you have
[tex]\begin{gathered} (x_1,y_1)=(-6,-4) \\ (x_2,y_2)=(-4,8) \\ m=\frac{8-(-4)}{-4-(-6)} \\ m=\frac{8+4}{-4+6} \\ m=\frac{12}{2} \\ m=6 \end{gathered}[/tex]Therefore, the slope of this line is 6.
