[tex]\displaystyle\bf\\\left \{ {{5x+3y=7 \ |\cdot 2} \atop {-2x+4y=-8 \ |\cdot 5}} \right. \\\\\\+\left \{ {{10x+6y=14} \atop {-10x+20y=-40}} \right. \\----------\\10x+6y-10x+20y=14-40\\\\26y=-26\\\\y=-26:26=-1\\\\2x=4y+8=4\cdot(-1)+8=-4+8=4\\\\x=4:2=2\\\\\\Otvet \ : \ (2 \ ; \ -1)[/tex]