Can you solve the below algebraic mathematical equation?

(J+O+I+N+T)3 = JOINT

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

Make a sentence consisting of three words that have the whole alphabet.

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see? What is it?

I have a head like a cat and feet like a cat, but I am not a cat. What am I?

Can you solve the maths in the below-given picture equation?

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

I am a normal creature, but I have five hands. I can even have more but even then I will be considered normal.

Who am I?

Find the missing number in the image below.

The great emperor Akbar once ruled India. He was well known for his intelligence. But along with that, he was known for the Nine Gems in his court. One of the nine gems was Birbal, a quick witted and extremely intelligent man. The stories of his wit were widely popular.

Once a king ruling in a distant land heard of Birbal. To check his wit, he sent an invitation and called him to visit his land. Akbar allowed Birbal to go and he took off on the journey.

Upon reaching that kings kingdom, he was welcomed with flowers. He was then escorted to the palace of the king. Upon entering the palace, Birbal found that there were six people sitting in front of him adorning the same robe. They were also lookalike and it was hard to judge who the real king was.

After a couple of minutes, Birbal approached one of them and bowed in front of him greeting him.

That was the real king. How did Birbal know who was the real king ?