Given the following system of linear equations: x1 + 2x2 + x3 = 4
12x1 + 16x3 = 28
8x1 - x2 + 5x3 = 12
(a) Write it in the form of Ax = b
(b) Find all solutions to the system using Gauss elimination method
(c) Use cramer's method to solve for x3 if possible.