L1 := {(x+3)/3 = y/(-2), y/(-2) = (z-7)/6}; L2 := {(x+6)/1 = (y+5)/(-3),(y+5)/(-3) =(z-1)/2};
  solve( L1 union L2,{x,y,z});
  n := crossprod([3,-2,6],[1,-3,-3]);
  Plane := innerprod(n,[x+9,y-4,z+5]) = 0;
  Plane := sort(Plane,[x,y,z]);
  with(plots):
  picL1 := spacecurve(evalm([-3,0,7]+t*[3,-2,6]),t=-5..5):
  picL2 := spacecurve(evalm([-6,-5,1]+t*[1,-3,-3]),t=-5..5):
  picPlane := plot3d( solve(Plane,z), x=-20..20, y=-15..15,grid=[5,5]):
display3d({picL1,picL2,picPlane});