How many tribes would be torn from Solomon's kingdom?

Answer: Ten

God said He would tear ten tribes away from Solomon's son.

“and said to Jeroboam, “Take ten pieces for yourself, for this is what the LORD, the God of Israel, says: ‘Behold, I will tear the kingdom out of the hand of Solomon, and I will give you ten tribes.”— 1 Kings 11:31 (BSB)