her savings is the 25% amount... well, if we take 65 to be the 100%, how much is 25% of that?
[tex]\bf \begin{array}{ccllll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
65&100\\
x&25
\end{array}\implies \cfrac{65}{x}=\cfrac{100}{25}[/tex]
solve for "x", that's her savings
the cost of the jeans is 65 - x