w - 3x + 4y - 3z = -5
-w + 8x - 4y + 18z = 15
Add the equations to get 5x + 15z = 10 So, x + 3z = 2.
w - 3x + 4y - 3z = -5
x + 3z = 2
Add 3 times the second equation to the first:
w + 4y + 6z = 1
x + 3z = 2
So, x = -3z + 2
w = -4y - 6z + 1
y = any real number (let y = s)
z = any real number (let z = t)
(w, x, y, z) = (-4s - 6t + 1, -3t + 2, s, t) = (1, 2, 0 ,0) + s(-4, 0, 1, 0) + t(-6, -3, 0, 1)