Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

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?

A woman lives in a skyscraper thirty-six floors high and is served by several elevators which stop at each floor going up and down. Each morning she leaves her apartment and goes to one of the elevators. Whichever one she takes is three times more likely to be going up than down. Why?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

Find the next number in the sequence

1, 2, 6, 21, 88, __?

Prove that the below maths equation is true.

8 + 8 = 91

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?

what one word does the below rebus identifies?

There are forty elephants and they have forty-fore heads. How can this be possible?

There was a greenhouse.
Inside the greenhouse, there is a white house.
Inside the white house, there is a red house.
Inside the red house, there are lots of babies.

What is It?