$a)$  

$\{\begin{array}{l}3x-5y=-19\mid \cdot \left(-2\right)\\ 2x+3y=0\mid \cdot 3\end{array}$  

$\{\begin{array}{l}-6x+10y=38\\ 6x+9y=0\end{array}\mid +$  

$19y=38\mid :19$  

$y=2$  

$\{\begin{array}{l}y=2\\ 2x+3y=0\end{array}$  

$\{\begin{array}{l}y=2\\ 2x+3\cdot 2=0\end{array}$  

$\{\begin{array}{l}y=2\\ 2x+6=0\mid :2\end{array}$  

$\{\begin{array}{l}y=2\\ x+3=0\mid -3\end{array}$  

$\{\begin{array}{l}y=2\\ x=-3\end{array}$  

 

 

$\underline{\underline{}}$  

 

 

$b)$  

$\{\begin{array}{l}6x-3y=18\mid :3\\ -2x+2y=-4\end{array}$  

$\{\begin{array}{l}2x-y=6\\ -2x+2y=-4\end{array}\mid +$  

$y=2$  

$\{\begin{array}{l}y=2\\ 2x-y=6\end{array}$  

$\{\begin{array}{l}y=2\\ 2x-2=6\mid +2\end{array}$  

$\{\begin{array}{l}y=2\\ 2x=8\mid :2\end{array}$  

$\{\begin{array}{l}y=2\\ x=4\end{array}$