For this you can use the slope formula, that is
[tex]\begin{gathered} m=\frac{y_2-y_1}{x_2-x_1} \\ \text{Where} \\ m\colon\text{ slope of the line} \\ (x_{1,}y_1)\text{ and }(x_{2,}y_2)\text{ are any two points on the line} \end{gathered}[/tex]
So, for example if you take (x1,x2) = (-4,2) and (y1,y2) = (-2,8), you have
[tex]\begin{gathered} m=\frac{y_2-y_1}{x_2-x_1} \\ m=\frac{8-2}{-2-(-4)} \\ m=\frac{8-2}{-2+4} \\ m=\frac{6}{2} \\ m=3 \end{gathered}[/tex]
Therefore, the slope of the line that contains these points is 3.
