Math Package to Solve Linear Equations?

["Thomas H. George" <lists@tomgeorge.info>]

I'm feeling stupid.  I used to have a math package which inverted 
matrices to solve systems of linear equations - i.e. enter the matrix 
and the y values and the program inverts the matrix and reports the x 
values.  I know how to do it manually but it is laborious for large 
matrices.  Perhaps Openoffice.calc/solver does this but it is not clear 
to me how to enter data for solver to do this.  apt-cache search matrix 
|grep inversion doesn't turn up anything.

Would someone please beat me over the head and point me to a simple 
package to do this job?

Tom George