For each of the following systems of linear equations, [1] rewrite the system in augmented matrix form, [2] use elementary row operations to find its equivalent reduced row-echelon form, and [3] deduce its solution, if the solution exists. [a] 2x y z = 5, -x + y + z = -4,2x + 2y + z = -2 [b] 2a + b 3c = -5, a - b +2c= 5,7a - b = 5 [c] 3r + 2st = 7,-2r + s + t = 5, -r + 4s + t = 12