Since we have a direct variation, we can use the following equation:
[tex]\frac{y}{x}=k[/tex]where k is the constant of variation.
If we use the point (6,18), then, we have:
[tex]\begin{gathered} (x,y)=(6,18) \\ \Rightarrow\frac{18}{6}=k \\ \Rightarrow k=3 \end{gathered}[/tex]now that we have that the constant of variation is k = 3, we can use this information to find n:
[tex]\begin{gathered} (x,y)=(n,-3) \\ k=3 \\ \Rightarrow-\frac{3}{n}=3 \\ \Rightarrow-3=3\cdot n \\ \Rightarrow n=-\frac{3}{3}=-1 \\ n=-1 \end{gathered}[/tex]therefore, n = -1
