Solving linear equations systems with > 9 variables accurately?

[Marcio]

Scilab - open source is quite similar to Matlab and can handle any kind of system you need. Linear, non-linear, complex... Name it!

This is how to enter data:

x = [1 2; 0 4];

y = [4 5; 9 1];

Type x/y on the command line and you'll get the result. How sweet is that? You could also store the data to any var you want:

z = x/y

EDIT: If dealing with large amounts of data, you could import them from excel or type them using the variable editor. If that is the case, create 'x' first, ie x=[] on the command line, and then double click it on the variables browser to start keying in data using a spreadsheet that is automatically created for that particular variable.
After getting the results on the screen, you'll want to format them, do so like this:

format('v',3+12)

Hope it helps!