Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

If "P" means "-", "Q" means "/", "R" means "+", and "S" means "*" then find the value of the following:

21 Q 7 R 9 S 10 P 13

In the Chess Board picture below white army is arranged. You need to add a black army on the board such that no piece is under any threat.
Note: Army comprised of 1 king, 1 queen, 2 rooks, 2 bishops, 2 knights, and 8 pawns.

The more you take me, the more you leave me behind.
Who Am I?

If an earthquake is 1 point higher on the Richter Scale than another earthquake which is actually 10 times stronger, how much stronger would an earthquake be if it was just half a point higher on the Richter scale?

John was piloting a plane behind a car but was never able to overtake it. Why?

Bay of Bengal is in which state?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

Which point will the car reach to go out?

Today, I celebrated my 32nd birthday but I was born in 1972.
How is this possible?