let's say that number is "x", so "x" is then the 100%.
we know 125 is the 500%, and "x" is the 100, what is "x"?
[tex]\bf \begin{array}{ccll} amount&\%\\ \cline{1-2} x&100\\ 125&500 \end{array}\implies \cfrac{x}{125}=\cfrac{100}{500}\implies \cfrac{x}{125}=\cfrac{1}{5} \\\\\\ 5x=125\implies x=\cfrac{125}{5}\implies x=25[/tex]
