A Game (spoiler!)

There's this game where a few people can't figure out the trick.
It kinda goes like this:
1) Pick a number in your head,
2) Double it.
3) Add 10
4) Divide it by 2
5) Subtract the original number.
The answer it 5.
Let me show you an example:
1) 7
2) 7 + 7 = 14
3) 14 + 10 = 24
4) 24 / 2 = 12
5) 12 - 7 = 5.
The trick is in step 3. You just take any number, and the answer half of it. 2, 1. 100, 50... etc