Ask them, “Could you please show me where in the bible it supports Solas Scriptura?”
It does not but they will refer to a passage that says it will be “profitable” to use scripture in defense. It does not say only! It says profitable.
Question #2 “before the bible was written, 354 (? exact date), what did the Christians use? If we were suppose to follow the bible alone, why did God have to come to earth, why not just hand us a bible?” Ok that is getting sarcastic, but it is true.
Now, my current favorite passage in scripture, 2Peter 3: 14-18.
"So, beloved, while waitting for this, make every effort to be found without stain or defilement, and at peace in his sight. Consider that our Lord’s patience is directed toward salvation. Paul, our beloved brother, wrote you this in the spirit of wisdom that is his, dealing with these matters as he does in all his letters. There are certain passages in them hard to understand. THE IGNORANT AND THE UNSTABLE DISTORT THEM TO THIER OWN RUIN.
You are forewarned, beloved brothers. Be on guard least you be led astray by the error of the wicked, and forfiet the security you enjoy. Grow rather in grace, and in the knowledge of our Lord and Savior Jesus Christ. Glory be to him now and to the day of eternity! Amen."
The caps were added by me and that is from the NAB bible.
You could also ask them where they got their bible from. Are they sure it is authentic? Do they hold the Catholic Church capable of producing a divinely inspired book? Because they got their book from us and then changed things!
You have the church and history in your side, you do not need to be afraid!
Good Luck and eventually agree to disagree! Then pray for them!!!