What can i do if my mom is 58 and was recently diagnosed with stage 3b lung cancer. how long does she have?

3b Ca Lung: Multiple factors determine how long a person lives. It depends on the nature of cancer and also what makes it 3b. Roughly 5 year survival of 3b is 10%. She can live up to 5 years, with a 10% chance of living beyond 5 years.

Depends: There are a variety of options for therapy available, including chemotherapy, radiation, surgery, immunotherapy, or combinations of all. Cures are possible. It is poor form to try to fix a time on what is a very treatable problem.