Locked by logic

Yushura waited outside the school and watched the math teacher leave the building. When the teacher stepped through the main gate, he noticed Yushura sitting in his car. He got into his own car, started it, and drove off. Yushura followed.

The teacher drove a bit further and took a turn onto a deserted road. Yushura followed him, and suddenly his own car disappeared; he found himself in a large room with no one present.

A loud voice came from the room: “If you want to leave this place and reach me, you must solve some math problems. There are 3 rooms in total. As you solve each problem, the door to the next room will open automatically. If you answer incorrectly, the current room will split in two, and you’ll have one extra room to traverse. The more mistakes you make, the smaller each room becomes and the more rooms you’ll have to navigate.”

“I haven’t lost my mind,” Yushura snapped. “I’ll just break this gate, find you, and then I will kill you.” 

Nothing happened when he tried to force the door open. After several unsuccessful attempts, exhausted and angry, he sat down on the floor. “Fine,” he said finally. “I’m ready. Tell me what to do.”

“Alright,” the voice replied. A question appeared on the wall: “If you multiply me by any number, the result is always the same. What number am I?”

“This is child’s play,” Yushura said proudly. “Zero.”. As soon as he spoke, the door opened and he moved into the next room.

“Ask your next question quickly,” he demanded.

The voice answered, and the next question appeared: “I am an odd number. Remove one letter and I become even. What number am I?”

Yushura froze. He thought and thought, but the answer didn’t come. “I don’t know,” he admitted at last.

“Do you concede?” the voice asked.

“Yes—tell me the answer,” Yushura said.

“Seven,” the voice replied. “Remove the ‘s’ from ‘seven’ and it becomes ‘even.’”

Frustrated, Yushura exploded, “What a ridiculous question! I’m done with this.”

“You must continue if you want to leave,” the voice said.

Immediately, the room split in two. The space became smaller and more cramped—now he had three rooms to pass through instead of two. The wrong answer had added an extra door between him and the teacher.

“Ask the next question,” Yushura said through gritted teeth.

The question appeared on the wall: ‘Pointing to a photograph, a man says, “Brothers and sisters, I have none, but that man’s father is my father’s son.” Who is in the picture?’

Yushura, in anger, said, "How do I know who's whose brother or sister? Let me go!"

“Think quietly and answer,” the voice insisted.

Yushura snapped," If he doesn't even know who's in the photo, how am I supposed to know? Who's his brother or sister or whatever?"

Yushura stared at the wall, confused and irritated. He replayed the sentence slowly in his head until it clicked. Unsure but desperate, he shouted, “I’ve got it—his son! The person in the photograph is his son.”