Find $x$ if $\begin{vmatrix} x & 3 \\ 12 & x \end{vmatrix} = \begin{vmatrix}5 & 3 \\ 12 & 5\end{vmatrix}$.

Explanation

1. 01

   The left side is $x^2 - 36$ and the right side is $-11$.

2. 02

   So $x^2 = 25$, $x^2 = 25$ and $x = \pm 5$.