What has 13 hearts but no other organs?

Can you tell a 3D object that has just two surfaces?

How many times can you subtract the number two from the number fifty?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

Three doctors said that Bill was their brother. Bill says he has no brothers. How many brothers does Bill actually have?

It can't be seen, can't be felt, can't be heard, and can't be smelt.
It lies behind stars and under hills, And empty holes it fills.
It comes first and follows after, Ends life, and kills laughter.
What is it?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

A deaf and mute man goes to the train station. Tickets for the train are 50 cents each. The man goes to the ticket booth and hands the man inside just a dollar. The man in the booth hands him two tickets.

How did the man in the booth know to give him two tickets without even looking at him?

Three people are in a room. Ronni looks at the Nile. The Nile looks at Senthil. Ronni is married but Senthil is not married. At any point, is a married person looking at an unmarried person? Yes, No or Cannot be determined.

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?