That would be impossible to know without the manuals for both systems or at least knowing if it were factory or custom install stereo... just too many possibilities. Unless I had the actual items in front of me, I couldn't even begin to hazard a guess.
From your previous posts it appears you have a Lancer? I looked over the stock radio wire diagrams, and there does not appear to be a mute wire on them. If you have an after market radio, check the diagram for that.