Find $x$ if $\begin{vmatrix} 2x & 5 \\ 8 & x \end{vmatrix} = \begin{vmatrix}6 & -2 \\ 7 & 3\end{vmatrix}$.

Explanation

1. 01

   The left side is $2x^2 - 40$ and the right side is $32$.

2. 02

   So $2x^2 = 72$, $x^2 = 36$ and $x = \pm 6$.