(7) Use the Gaussian elimination method to determine whether each of the following linear sys- tems has no solution, a unique solution, or an infinite number of solutions. Write all the solutions. (a) 2x1 + 12 - 13 = 1 (b) 1 + 12 + 13 = 4 (c) + 12= 1 x1 + 212 - 13 = 1 m1 + X2 = 6 2x1 + 12 = 3 - X1 - 212 + 2x3 = 2 3x1 + 212 = 4