Find all solutions to the following systems of linear equations. (a) x1 2x2 + 2x3 = 5 x1 x2 = 1 x1 + x2 + x3 = 5 (b) x1 + x2 + 3x3 = 3 x1 + x2 + x3 = 1 2x1 + 3x2 + 8x3 = 4