[tex]\displaystyle \left \{ {{2x+y=7} \atop {2y-x=4}} \right. \\\\\left \{ {{y=7-2x} \atop {2y-x=4}} \right. \\\\2(7-2x)-x=4\\x=2\\y=7-2*2\\y=3\\(x,y)=(2,3)[/tex]