Linear systems

 

In Mathematica

For comparison with other CAS choose from: Axiom Derive Macsyma Maple Reduce

inputs outputs

    Solve[2 x1 +   x2 + 3 x3 - 9 == 0,
             x1 - 2 x2 +   x3 + 2 == 0,
           3 x1 + 2 x2 + 2 x3 - 7 == 0, x1, x2, x3 ]

    {{x1 -> -1, x2 -> 2, x3 -> 3}}