I've seen both banking and consulting analysts try to solve this exact problem in excel. The ambitious ones will use circular references and let excel find the

I've seen both banking and consulting analysts try to solve this exact problem in excel. The ambitious ones will use circular references and let excel find the fixed point. In (good) excel, most formulas you write have a clear input => output relationship. Solving a system of equations (no matter how simple) breaks this relationship down. I suspect a similar thing happens when programming.