Solve the below puzzle by replacing the question mark with the correct number.

3 6 12

4 8 16

5 10 ?

Find the value of "?" in the ball picture Riddle below:

When I asked a girl's name she told me her name is the date '07/09/2001'.

I thought for a few seconds and then I got her name. Do you?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Cristina leaves home and then she makes exactly 3 left turns and returns home where she found 2 girls wearing the mask.

Who are these two masked girls?

Why is 6 afraid of 7?

A man dies of old age on his 25 birthday. How is this possible?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

John was a very careless driver, so his owner Jacob gave him an offer that he will get an incentive of Rs.30 for every bottle box he delivered without breaking it and he will be charged Rs.90 for every bottle box he broke. Jacob gave John 100 bottles-box to deliver. After delivery, Jacob paid John Rs.2400. How many bottles-box did John break?

Spot what is wrong here in below Picture?