Hello everyone
I created the following program or whatever you call it and compile it with no error, however I got zeros in my z solution
Positive variable x1, x2, x3;
free variable z;

Hi
There is nothing wrong with your solution: you have three less-than-or-equal constraints and a to minimize objective equation all with positive coefficients.
This means that {0,0,0} is the minimal and optimal solution. All constraints are met and the objective variable is minimized.
Perhaps you meant greater-than-or-equal in your constraints.

Hi
This is the optimal solution imagine a one-dimensional problem: x<5 and z=3x. 0 is the optimal solution.
It would make more sense if you would have >= constraints.
Cheers
Renger