Given two points
[tex](x_1,y_1),\quad (x_2,y_2)[/tex]
The slope of the line passing through both is
[tex]m=\dfrac{\Delta y}{\Delta x}=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
Plugging your values, we have
[tex]m=\dfrac{7-3}{8-1}=\dfrac{4}{7}[/tex]
