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

Count the number of lines in the image below ?

A time long back, there lived a king who ruled the great kingdom of Trojan House. As a part of the renovation of the kingdom to meet future security needs, he asked his chief architect to lay down a new play in a manner that all of his 10 castles are connected through five straight walls and each wall must connect four castles together. He also asked the architect that at least one of his castles should be protected with walls. The architect could not come up with any solution that served all of King's choices, but he suggested the best plan that you can see in the picture below. Can you find a better solution to serve the king's demand?

You can take four of the five letters out of this word, but the pronunciation never changes. What is the word?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

Can you make four (4) nines (9) equal 100?

I am an odd number. Take away a letter and I become even. What number am I?

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

What does this simple rebus mean?

In the city of Brain Teasers, 5% of people do not list their phone numbers. Now if we select random 100 people from the phone directory, then how many people selected will have unlisted phone numbers?