250 is the number youre looking for
is 10% of "x", meaning "x" is the 100%, and we know that 25 is 10%, so
[tex]\bf \begin{array}{ccll}amount&\%\\\cline{1-2}x&100\\25&10\end{array}\implies \cfrac{x}{25}=\cfrac{100}{10}\implies \cfrac{x}{25}=10\implies x=250[/tex]