Replace the question mark with the correct number in the below-given picture?

There are three boxes on a table. One of the box contains Gold and the other two are empty. A printed message contains in each box. One of the message is true and the other two are lies.

The first box says "The Gold is not here".

The Second box says "The Gold is not here".

The Third box says "The Gold is in the Second box".

Which box has the Gold?

An artist while painting a scenic beauty, decides to paint three layers of blue colour on the sky.

Which layer will go on the first?

Teacher ask the student

'Why are you standing on that chair in music class ?'.

what did student replied ?

What do you answer even though it never asks you questions?

Replace the question mark with the number below given a simple math problem.

I have Rs.50 and I spend it in the way as below.

I have a clock(12-hour format) and both the needles of the clock overlap at 12:00.
After how much time, they will overlap again?

How many bananas can you eat if your stomach is empty?

An exterior architect is asked by a builder to plant seven trees in a manner that there are exactly six rows of trees in a straight line and each row has three trees in particular.

How will he do it?