When the problem can never be resolved, you redefine the problem until you find a version of the problem with a good solution. So if the problem is that software is hard to estimate, which is hard, we redefine the problem to something like “I want to be able to ship something people want to buy, before we run out of money” or “I want to ship a game in time for Christmas” or “I want to reduce operating costs so we don’t drown in debt.”

Incidentally, the process of writing a software program is often the same process—redefining the problem until you find a problem with a good software solution, rather than finding a hard problem and throwing software at it until you die from exhaustion.