I think that's a problem with mathematics, not with programming languages. When you define a new type of number, and you want to be able to use it in arithmetic operations with other numbers, you have to define what the outcome will be.

Mathematicians are a bit sloppy about this sometimes because they except you to know what the right thing is, but if they aren't sloppy have to go through the same motions as somebody who writes a class for a new numeric type in Perl 6.

So of course you are right in the sense that Perl 6 doesn't solve a problem that's not yet solved in mathematics, but I think it might be a bit too optimistic to really expect that ;-)