Which number should replace the question mark?

What are the 50th, 63rd and 100th numbers in the sequence below?
4, 5, 8, 8, 9, 9, 12, 13, 13, 13, 17, 18, ...

Take 9 from 6, 10 from 9, 50 from 40, and leave 6.

How Come ??

In the image below, can you find the value of an angle(y)

What makes this number unique: 8,549,176,320?

A 3 digit number is such that it's unit digit is equal to the product of the other two digits which are prime. Also, the difference between it's reverse and itself is 396.

What is the sum of the three digits?

When it's bad luck to meet a black cat?

Consider all the numbers between 1 and 1 million. Among all these numbers, there is something very special about the number 8 and the number 2202. What is it?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

why number 8549176320 is one of a kind?