Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

This is a classy optical illusion puzzle. What more you can find except bricks in the image below?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

How do you go from 98 to 720 using just one letter?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

No one wants to have it, but if one got it, he does not want to lose it. What is It?

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?

What came first, the chicken or the egg?

How high do you have to count before you use the letter “a” in the English spelling of the whole number?

With the help clues provided in the image, can you find the 5 digit key?