$$\left. \begin{array} { l } { a = s , b = 3 , c = 9 } \\ { a + b + c } \end{array} \right.$$
$s=d-12$
$a=d-12$
$b=3$
$c=9$
$d\in \mathrm{C}$
$s=d-12$
$a=d-12$
$b=3$
$c=9$
$d\in \mathrm{R}$
