To find the constant of proportionality, we use the following formula
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]Where,
[tex]\begin{gathered} x_1=3 \\ x_2=6_{} \\ y_1=45.75 \\ y_2=91.50 \end{gathered}[/tex][tex]m=\frac{91.50-45.75}{6-3}=\frac{45.75}{3}=15.25[/tex]