[tex]\bf \begin{array}{ccllll}
cm&mm\\
\textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\
1&10\\
x&31
\end{array}\implies \cfrac{1}{x}=\cfrac{10}{31}[/tex]
solve for "x"
