$$\left. \begin{array} { l } { \begin{array} { l } { x y + 4 x + 3 y + 12 } \\ { a x - 5 a + 4 x - 20 } \end{array} } \end{array} \right.$$
$\left(x+3\right)\left(y+4\right),\ \left(x-5\right)\left(a+4\right)$
