[tex]\displaystyle \left \{ {{x-y=5} \atop {x+2y=-1}} \right.\\ \\\left \{ {{x=5+y} \atop {x+2y=-1}} \right. \\\\5+y+2y=-1\\y=-2\\x=5+(-2)\\x=3\\(x,y)=(3,-2)[/tex]