[tex]\displaystyle\\\left \{ {{3x-2y=21|\times2} \atop {3x+4y=3}} \right. \\\\\left \{ {{6x-4y=42} \atop {3x+4y=3}} \right. \\\\(1)+(2)=6x+3x+4y-4y=42+3\\9x=45\\x=5= > y=-3[/tex]