solving equations involving matrices



Hello, I am somewhat new to Maxima. I am trying to solve this simple 
system of linear equations:

3x + 8y = 5
4x + 11y = 7

I put them into a matrix and tried to solve:

(%i19) matrix([3,8],[4,11]) . matrix([x],[y]) = matrix([5],[7]);

                             [ 8 y + 3 x  ]   [ 5 ]
(%o19)                      [            ] = [   ]
                             [ 11 y + 4 x ]   [ 7 ]
(%i20) solve(%,[x,y]);

(%o20)                                []

This somewhat disappointed me, because when I did:

(%i18) solve([3*x + 8*y = 5, 4*x + 11*y = 7],[x,y]);

(%o18)                        [[x = - 1, y = 1]]

it seemed to work fine. Am I doing something wrong? Why doesn't Maxima 
have an answer for the equation involving matrices?