Can you replace the question mark with the correct number?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

Spot 5 differences in two Christmas tree below:

There is a place where if I stand up straight, I will still be considered sideways.

Why do you find that most of the buildings are deprived of the 13th floor?

Below toothpicks/matchsticks indicate the group of fishes moving from west to east direction. Can you make them move from east to west by just moving three toothpicks/matchsticks?

Christina is older than Kareena and Karishma. Katrina is older than Karishma and younger than Kareena. If Kareena has a brother named John, who is older than Christina, who's the youngest?

Find the number of squares in the below picture

Find the hidden tiger in the given optical illusion ?

An explorer goes on an exposition in the jungle. He sets up camp in the middle of the jungle. The next morning he sees something with a head and a tail, but he is not afraid. What did he see in his bag?