Answer :

For any two points (x1, y1) and (x2, y2)

[tex]\text{slope =}\frac{y_2-y_1}{x_2-x_1}[/tex][tex]\Rightarrow\text{slope=}\frac{7-5}{8-4}=\frac{2}{4}=\frac{1}{2}[/tex]