(a) Apply Gauss's Method to the left-hand side to solve
x + 2y - w = a
2x + z = b
x + y + 2w = c
for x, y, z, and w, in terms of the constants a, b, and c.
(b) Use your answer from the prior part to solve this.
x + 2y - w = 3
2x + z = 1
x + y + 2w = -2