Thanks a lot

A := Matrix([[5, 4, 5, 4, 8, 4, 6, 1, 4], [2, 8, 4, 7, 5, 1, 9, 6, 1], [8, 4, 9, 8, 8, 8, 6, 2, 8], [7, 1, 8, 6, 6, 5, 3, 7, 7], [8, 7, 9, 4, 7, 8, 2, 7, 4], [5, 1, 7, 8, 5, 7, 2, 2, 8], [7, 4, 1, 7, 7, 1, 7, 8, 6], [2, 9, 9, 4, 7, 5, 2, 6, 8]]);

Create the vector b that is column 7 from A and the matrix C that is made from columns 1 to 6 and 8 to 9 of A (in the same order as the columns of A