Given that, 2x+y−z=7 . . . (i) x−3y+2z=1 . . . (ii) x+4y−z=5 . . . (iii) and From Eqs. (i) and (ii), 5x−y=15 . . . (iv) From Eqs. (i) and (iii), 5x−y=16 . . . (v) Equation (iv) and (v) shows that they are parallel and solution does not exist.