At first glance, this looks like a simple math puzzle, but the wording is designed to trick you.
The Puzzle:
I enter a room with 50 people.
A killer walks in and kills 30.
How many people are still in the room?
Answer: 52
Explanation:
You entered the room, so that’s 1 person.
There were already 50 people inside.
A killer enters, adding 1 more person.
That makes 52 people in the room before the attack.