r1:x+2*y=0;

linsolve([r1],[x,y]);

load(draw)$

wxdraw2d(xaxis=true,yaxis=true,color=red,implicit(r1,x,-10,10,y,-10,10));

r2:x+2*y=3;

linsolve([r2],[x,y]);

wxdraw2d(xaxis=true,yaxis=true,color=blue,implicit(r2,x,-10,10,y,-10,10));

wxdraw2d(xaxis=true,yaxis=true,color=red,implicit(r1,x,-10,10,y,-10,10),color=blue,implicit(r2,x,-10,10,y,-10,10));