40 hrs at 8 bucks, 40*8 or 320, now, is 2 workers, so 320+320 or 640
so... how much is 640 from 2000 in percentage? well, if we take 2000 as the 100%, then [tex]\bf \begin{array}{ccllll}
amount&\%\\
\textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\
2000&100\\
640&x
\end{array}\implies \cfrac{2000}{640}=\cfrac{100}{x}[/tex]
solve for "x"