To solve your linear equation, type in

simultd([2,3;-8,-12],[6;-24]) then ENTER.

You should get Error:Singular Matrix.

That's because one is a multiple of the other. There both essentially the same.

Another way is to use RREF([2,3,6;-8,-12,-24]).

You should get a row of 0's at the bottom. That' no good.