% how many solutions
D=[1,2,3,3;5,6,7,11]
E=[1,2,3,3;5,6,7,11;1,1,1,2]
E(2,:)=E(2,:)-5*E(1,:)
E(3,:)=E(3,:)-E(1,:)
E(2,:)=E(2,:)/(-4)
E(3,:)=E(2,:)+E(3,:)
E(1,:)=E(1,:)-2*E(2,:)
%infinitely many