We know that:
- y varies directly as x
- y = 6 when x= 3
And we must find y when x = 9
To find it:
1. we must use that y varies directly as x
[tex]y=kx[/tex]2. We must find k using that y = 6 when x = 3
[tex]\begin{gathered} 6=k\cdot3 \\ k=\frac{6}{3} \\ \Rightarrow k=2 \end{gathered}[/tex]3. Finally, to find y when x = 9 we must replace x = 9 and k = 2 to solve it for y
[tex]\begin{gathered} y=2\cdot9 \\ y=18 \end{gathered}[/tex]ANSWER:
y = 18 when x = 9
