[tex]\bf \begin{array}{llllll}
\textit{something}&&\textit{varies inversely to}&\textit{something else}\\ \quad \\
\textit{something}&=&\cfrac{{{\textit{some value}}}}{}&\cfrac{}{\textit{something else}}\\ \quad \\
y&=&\cfrac{{{\textit{k}}}}{}&\cfrac{}{x}
\\
&&y=\cfrac{{{ k}}}{x}
\end{array}\\\\
-----------------------------\\\\
\textit{now, we know that }
\begin{cases}
y=120\\
x=7
\end{cases}\implies 120=\cfrac{k}{7}[/tex]
solve for "k", to find "k" or "constant of variation"
