`12^{2} - 4 . (x - 5) = 2^{3} . 3^{2}`
$\Rightarrow$ `144 - 4 . (x - 5) = 8 . 9`
$\Rightarrow$ `144 - 4 . (x - 5) = 72`
$\Rightarrow$ `4 . (x - 5) = 144 - 72`
$\Rightarrow$ `4 . (x - 5) = 72`
$\Rightarrow$ `(x - 5) = 72 : 4`
$\Rightarrow$ `x - 5 = 18`
$\Rightarrow$ `x = 18 + 5`
$\Rightarrow$ `x = 23`
$\text{Vậy}$ `x = 23`