so, if we take 685 to be the 100%, what is 20.55 in percentage off of it?
well [tex]\bf \begin{array}{ccllll}
amount&\%\\
\textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\
685&100\\
20.55&x
\end{array}\implies \cfrac{685}{20.55}=\cfrac{100}{x}[/tex]
solve for "x"
