the constant of proportionality is simply the slope of the relation, and to find the slope, all we need is two points off the table.
[tex]\bf \begin{array}{|c|c|c|c|c|l} \cline{1-5} Bouquets&3&6&9&12\\ \cline{1-5} Price&9&18&27&36 \\ \cline{1-5} \end{array}\qquad \qquad (\stackrel{x_1}{3}~,~\stackrel{y_1}{9})\qquad (\stackrel{x_2}{9}~,~\stackrel{y_2}{27}) \\\\\\ slope = m\implies \cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{27-9}{9-3}\implies \cfrac{18}{6}\implies 3[/tex]
