[tex]\bf \qquad \qquad \textit{inverse proportional variation} \\\\ \textit{\underline{y} varies inversely with \underline{x}} ~\hspace{6em} \stackrel{\textit{constant of variation}}{y=\cfrac{\stackrel{\downarrow }{n}}{x}~\hfill } \\\\[-0.35em] \rule{34em}{0.25pt}[/tex]
[tex]\bf \stackrel{\textit{"j" varies inversely with "k"}}{j = \cfrac{n}{k}}\qquad \qquad \textit{we also know that } \begin{cases} k=3\\ j=12 \end{cases} \\\\\\ 12=\cfrac{n}{3}\implies 36=n~\hfill \boxed{j=\cfrac{36}{k}} \\\\\\ \textit{when j = 18, what is \underline{k}?}\qquad 18=\cfrac{36}{k}\implies k=\cfrac{36}{18}\implies k=2[/tex]
