Welcome to the forum, glad you joined.
I don't find the search feature on this forum to be very easy so never hesitate to ask a question even if you think it has been asked many times before. If you can fined old threads on a topic great, but a specific question may be good too, your circumstances may be different. Besides, repeat questions are often easier to answer.
There is no good answer to your question because of all those variables. Many are lost to predators. Disease and parasites get a lot. The older the chicken the more likely disease is. Some just break down. Some are injured or become non-productive so they are removed. That could be killing or rehoming. Many of us raise them for meat, those don't live long. Some of us play with breeding and genetics, that requires a constant turnover.
I don't know what the official record is for how long a chicken can live, I've seen reports on here of some living for 15 years. But due to all the variables the average is going to be a lot less. I'm not going to guess. But once again,