Start identifying the proportionality constant using one of the points of the graph, then:
[tex]\begin{gathered} y=k\cdot x \\ 2=k\cdot8 \\ k=\frac{2}{8} \\ k=\frac{1}{4} \end{gathered}[/tex]
then, use the value found to obtain the cost for 20 cookies
[tex]\begin{gathered} y=\frac{1}{4}x \\ y=\frac{1}{4}\cdot20 \\ y=5 \end{gathered}[/tex]
20 cookies cost $5.00
Finally, we can find the graph corresponds to a proportional relationship since it is a straight line and it also passes through the origin
