\(\dfrac{x-3}{-25}=\dfrac{-4}{x-3}\)
\(\Rightarrow\left(x-3\right)\left(x-3\right)=\left(-4\right).\left(-25\right)\)
\(\Rightarrow\left(x-3\right)^2=100\)
\(\Rightarrow\left(x-3\right)^2=10^2\)
\(\Rightarrow\left[{}\begin{matrix}x-3=10\\x-3=-10\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=13\\x=-7\end{matrix}\right.\)