Getting out of Credit Card Debt

I attended your Zoom lecture last night and was very glad I did. You clarified many things, and I seem to be on the right track. I am a new widow (after 56 years of marriage), and money is now my concern, especially with all the things going on in our government. I am a Chicken$ person and seem to be doing what is correct. My question is: I missed your explanation about the 72 thing you talked about. Can you write back to me and explain it again? My son, who lives in Boston, got into big debt with his credit cards. I want to share the advice you gave us in your talk last night.