Use the inverse of the matrix to decode the cryptogram:

51 72 27 38 27 36 38 57 59 81 42 61

Divide the message into groups
of two (the matrix A is a 2 x 2) to form the coded row matrices and multiply
each coded row matrix by A^{-1} on the right.

Find A^{-1}

Divide the message into groups
of two (the matrix A is a 2 x 2) to form the coded row matrices and multiply
each coded row matrix by A^{-1} on the right.

Thus, the message is: