that's must be 4 because divide by zero.
1. there's no even prime numbers excludeing 2. so, the solution set is none {}.
2. "evenly" is the x^2/sizeof(x). however, the size of x is zero.
It's just like customers never visit the resturant, you can't tell which one of them love the food or not.
I claim it's how we describe categories of things.
No math needed...
[following added in edit]
In the case of the restaurant that has no customers,
ALL of the customers love the food. Because you can't find ONE that doesn't. and ...
NONE of the customers love the food. Because you can't find ONE that does.
It's logically ok to use universal quantifiers [all, no, none] with empty sets.
But you can't use particular quantifiers [one, some] with empty sets.
