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

Find the missing letter in the last circle logically in the given below picture.

A boy and a girl are sitting on the porch.
"I'm a boy," says the child with black hair.
"I'm a girl," says the child with red hair.
If at least one of them is lying, who is which?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?

I know a 5-digit number having a property that With a 1 after it, it is three times as large as it would be with a one before it.

Guess the number?

When can we add 2 to 11 and get 1 as the correct answer?

I have an eye but still cannot see.

Who am I?

What is the coolest letter in the alphabet?

What jumps when it walks and sits when it stands?

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?