3x+2y+-5 = -4x+2y+-7

Just an example

It appears the two programs are working after I installed Doors CSE 8.1 per Unicorn's suggestion! I'm going to try to work some equations using Cramer's Rule, a program I installed. I will let you know how it goes in a sec.

Well, that problem with the matrices is very simple to solve, because you entered "-2" with the minus of the substraction, which will throw an error, because that is not possible. You must use the minus of the negative value, sometimes also written as "~" (for a simple example: see this). So, do not use "-2" but "~2", that minus sign is between the enter and the point.

Secondly, that program you downloaded works good for me:

See also this:

It occurs to me that you may be mixing up the negative and subtraction signs. Make sure you use the [(-)] key for negation and the [-] key for subtraction. My apologies if this is something with which you're already familiar.