If 21x = 79x, what is the value of x?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

A girl was sitting in her hotel room when she heard a knock on the door. She opened the door and found that a man was standing outside.
The man said, "Oh! I am really sorry, I thought this was my room."
He then walked through the corridor to the elevator. The girl did not know the man. She closed her door and called security asking them to apprehend the man.
What made her suspicious of that man? He might have been genuinely mistaken.

I am not a bull but I have horns.
I am not an ass but I have a pack saddle.
Wherever I go, I leave silver behind me.

Who am I?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

The captain of a ship is telling you an interesting story and then poses a question. He says, “I have travelled the oceans far and wide. One time, two of my sailors were standing on opposite sides of the ship. One was looking west and the other one east. And at the same time, they could see each other clearly. Can you tell me how that was possible?”

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

By using 'because' continuously three times, can you make an English statement ?

In my garden, I have many trees but only one of them is the mango tree. In these mango trees, there are some mangoes(as expected).

But after a strong wind, there are neither mangoes on the tree nor on the ground. Explain?