Ok 2x + y - z = 7 -2y +3z = -15 x + 2y - 5z = 17 combine 2nd 3rd x - 2z = 2 x = 2z + 2 double first statement 4x + 2y - 2z = 14 combine with second statement 4x + z = -1 substitute 2z + 2 for x 8z + 8 + z = -1 combine like terms 9z + 8 = -1 sub 8 from both sides 9z = -9 divide both sides by 9 z = -1 substitute -1 for z in second statement -2y - 3 = -15 add 3 to both sides -2y = -12 divide both sides by -2 y = 6 substitute -1 for z into the fifth statement x = -2 + 2 x = 0
