Can you replace the question mark with the correct letter?

6 + 6 + 6 = N
7 + 7 + 7 = E
8 + 8 + 8 = R
0 + 0 + 0 = ?

how come the second man dies?

There was a strange boy who was born before his father. How can this be possible?

What's a single-digit number with no value?

You have $100 with you and you have to buy 100 balls with it. 100 is the exact figure and you can't go below or above the numbers and you have to use the entire $100. If there is no kind of tax applied how many of each of the following balls will you be able to buy:

Green Balls costing $6
Yellow Balls costing $3
Black Balls costing $0.10

Now, how many of each must you buy to fulfil the condition given?

What always comes into a house through the keyhole?

Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

In the figure, you can see nine stars. What you have to do is connect all of them by using just four line and without lifting your hand i.e. in a continuous flow.

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

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?