C = [1 -3 0 5; -1 1 5 2; 0 1 1 0]
C(2,:)=C(2,:)+C(1,:)
C([2,3],:)=C([3,2],:)
C(3,:)=C(3,:)+2*C(2,:)
C(3,:)=(1/7)*C(3,:)
C(2,:)=C(2,:)-C(3,:)
C(1,:)=C(1,:)+3*C(2,:)

