Sorry, no "canceling" after junior high. And no dividing by zero before or after junior high.
Students are usually taught by their teachers to "cancel" things, and they forget the actual mathematical operation they're doing. Couple that with being so used to playing with variables, forgetting they stand for actual (oops, almost said "real") numbers, and most people fall for this joke.
Speaking of "real," more geek humor: "God is real, unless declared integer."
20 points to any old-timers who get that one.