most difficult math problem
I've had a batch of math classes, and so far, the most difficult IMO is differential equations. Lots of plug-and-chunk, and that's the problem for me: most of the time I don't know where to plug things.
The Beal Conjecture isnât the first math problem whose solution was tied to a big cash prize. In 2000, the Clay Mathematics Institute in Cambridge, Mass., allocated seven $1 million prizes for problems now known as Millennium Problems.