Solve the following systems of equations by Gaussian Elimination:
(a) x1 - 2x2 + 2x3 = 15
x1 - 2x2 + x3 = 10
2x1 - x2 - 2x3 = -10
(b) 2x1 - x3 = 1
- 4x1 + 2x3 - 3x3 = -8
x1 - 3x2 + x3 = 5
(c) x2 - x3 = 4
-2x1 - 5x2 = 2
x1 + x3 = -8
(d) a - y + z - w = 0
-2a + 2y - z + u> = 2
-4a + 4y + 3z = 5
x1-3y + w= 4
(e) -3x2 + 2x3 = 0
x3 - x4 = 2
x1 - 2x3 = -1
- 4x1 + 7x4 = -5