Here is another interesting one, but I doubt it is a brain teaser. It is more of a trick.
I would like for whoever reads this to pick a number from 1-infinite, DO NOT POST YOUR NUMBER.
Now, multply your number by 2, add 6, divide by 2 and, subtract by the number you originally picked.
When you are ready with your answer, post ready. DO NOT POST YOUR ANSWER.
After that I will post all your answers. You all will probably figure this out.
If you know this trick, don't ruin it.