The teacher asks little Johnny, "If I give you two cats, and Jimmy gives you two more, and Sally gives you two more, how many cats would you have?"

Johnny thinks about it for a few seconds and says, "Seven."

The teacher says, "No, let's try again. Listen carefully. I give you two, Jimmy gives you two more, and then Sally gives you two more."

Johnny spends a few minutes thinking it out, and again says, "Seven."

The teacher says, "Let's try it another way. If I put two apples on your desk, then two more, and then two more, how many apples would you have?"

Johnny says, "Six."

The teacher says, "Good, now if I give you two cats, and Jimmy gives you two more, and then Sally gives you two more, how many cats would you have?"

Johnny again says, "Seven."

The teacher, obviously frustrated, yells at Johnny, "Why do you keep saying seven?!"

Johnny says, "Because... I've already got a cat!"

~>^..^<~