the old fare was "x"
then it got bumped up by 15%, and the new price is x + 15% of x,
so.. one could say, that "x" is the 100%, then you add a 15% to
it, to get 600
thus [tex]\bf \begin{array}{ccllll}
amount&\%\\
\textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\
x&100\\
600&100+15
\end{array}\implies \cfrac{x}{600}=\cfrac{100}{100+15}[/tex]
solve for "x"
