You cannot divide, you must multiply your matrix by the inverse of the other matrix (or multiply the inverse by your matrix - note that the order you do it is important for matrices - IGYKT).
ALso, not all matrices have inverses, so this area can be a can of worms if your matrix turns out to be the awkward type. There exist numerous methods for determining an inverse and whether one exists - you will have to find and link to a library which contains a suitable matrix-inversion routine, possibly one tailored to your specific type of matrix (e.g. symmetric, non-symmetric, block diagonal, real, complex, sparse, ill-conditioned, or any combination of these). Good luck.
