Find the errors in james work solving the sydtem with elimination

(1) 2x+ y - z = 0 (2) 4x - 2y +z = 11 (3) 6x+ y - 2z = 5 (4) 6x - y = 11 Adding Lines 1 + 2 to eliminate z (5) 14x - 3y = 27 Adding 2 times line 2 plus line 3 to eliminate z (6) -18x +3y = 33 Multiply line 4 by -3 (7) -4x = 60 Add line 6 to line 5 (8) x = -15 Divide both sides by -4 (9) 6*(-15) - y =11 Substituting x value into line 4 (10) -90 - y = 11 Simplifying (11) y = 101 (12) 2"(-15) + (101) - z= 0 Substituting x and y values into line 1 (13) 71 = z (-15, 101, 71) O James did not check his answer in the other equations. James forgot the negative sign in front of x on line 8 James only multiplied the 11 by 3, not -3 on line 6 O) James did not distribute the 2 fully on line 5 multiplication