[tex]\displaystyle \left \{ {{0,5x-y=0,5} \atop {x-2y=1}} \right.\\ \\\left \{ {{y=-0,5+0,5x} \atop {x-2y=1} \right. \\\\x-2(-0,5+0,5x)=1\\x\in R\\(x,y)=(x,-0,5+0,5x),x \in R[/tex]