Truly, this is the mind-bender of the age.
Forget the Riddle of the Sphinx. Forget how Adam Sandler still has a career. This is the question that will drive mankind insane.
Behold.
Now, when you actually write it down, it makes more sense.
Thirty cows in a field, twenty ATE chickens. How many didn't?
Get it now? Simples. Now go off and baffle your friends and take a video while you're at it.
Via YouTube