Answer :
Direct proportionality:
[tex]y=kx[/tex]
k - the constant of proportionality
[tex]y=2 \hbox{ when } x=3 \\ \Downarrow \\ y=kx \\ 2=3k \\ k=\frac{2}{3} \\ \\ y=? \hbox{ when } x=9 \\ \Downarrow \\ y=kx \\ y=\frac{2}{3} \times 9 \\ y=2 \times 3\\ y=6 \\ \\ \boxed{y=6 \hbox{ when } x=9}[/tex]
[tex]y=kx[/tex]
k - the constant of proportionality
[tex]y=2 \hbox{ when } x=3 \\ \Downarrow \\ y=kx \\ 2=3k \\ k=\frac{2}{3} \\ \\ y=? \hbox{ when } x=9 \\ \Downarrow \\ y=kx \\ y=\frac{2}{3} \times 9 \\ y=2 \times 3\\ y=6 \\ \\ \boxed{y=6 \hbox{ when } x=9}[/tex]
