Every few months, the Internet eats itself over some kind of viral riddle or illusion, each more infuriating than the last. And so, like clockwork, this maddening math problem has gone viral, ...

You don’t have to be a math whiz to know that 4 - 2 + 1 equals 3. Yet I was working with several students recently who said it equals 1. And it wasn’t their fault. Nor was it their teacher’s fault.