What does below rebus means ?

I add 5 to 9 and get 2. The answer is correct, so what am I?

Here is a conversation between a couple who both are software professionals.

Husband: Hey! What is your date of birth?
Wife Replied Angrily: It is 591062400
Husband after doing some calculations replied, "Got It".

What is the DOB of the wife?

In the picture given below, can you find out which digit will take place of the question mark?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

I have feet, but no legs. Which animal Am I?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Which city is three-fifths chick two third cat and 50% goat?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

Three cars are driving on a track that forms a perfect circle and is wide enough that multiple cars can pass anytime. The car that is leading in the race right now is driving at 55 MPH and the car that is trailing at the last is going at 45 MPH. The car that is in the middle is somewhere between these two speeds.
Right now, you can assume that there is a distance of x miles between the leading car and the middle car and x miles between the middle car and the last car and also, x is not equal to 0 or 1.
The cars maintain their speed till the leading car catches up with the last car and then every car stops. In this scenario, do you think of any point when the distance between any two pairs will again be x miles i.e. the pairs will be x distance apart at the same time ?