In a school, there are four subjects. Seventy percent of students study English, seventy five percent of students study Science, eighty five percent of students study Mathematics and eighty percent of students study Spanish.

Can you calculate the percentage of students that study all four subjects?

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.

Can you spot the hidden girl in the picture below?

If 24H in a D => 24 hours in a day.
What does "64S on CB" stand for?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

You can see it everyday, But cannot touch it at will. What is it?

Can you make the below equation true by using any three numbers from "1, 3, 5, 7, 9, 11, 13 and 15"?

( ) + ( ) + ( ) = 30

What can you see in the middle of March and April that you can never see in any other month?

In a competitive exam, each correct answer could win you 10 points and each wrong answer could lose you 5 points. You sat in the exam and answered all the 20 questions, which were given in the exam.
When you checked the result, you scored 125 marks on the test.

Can you calculate how many answers given by you were wrong?