\(\dfrac{x-1}{-15}=\dfrac{-60}{x-1}\\ \Rightarrow\left(x-1\right)^2=-15\cdot\left(-60\right)\\ \Rightarrow\left(x-1\right)^2=900\\ \Rightarrow\left[{}\begin{matrix}x-1=30\\x-1=-30\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=31\\x=-29\end{matrix}\right.\)