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

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

What does this rebus mean?

O
N
C
E
TIME

Which statement is true out of the following?
One statement here is false.
Two statements here are false.
Three statements here are false.

Which alphabet letter is a question?

A beggar on the street can make one cigarette out of every 6 cigarette butts he finds. After one whole day of searching and checking public ashtrays the beggar finds a total of 72 cigarette butts. How many cigarettes can he make and smoke from the butts he found?

Can you solve this picture maths equation?

I am not alive, but I grow; I don't have lungs, but I need air; I don't have a mouth, but water kills me. What am I?

Solve the equation in the image by looking at the pattern closely.

On a bright sunny day, two fathers took their son fishing in the lake. Each man and son were able to catch one fish. When they returned to their camp, there were only three fishes in the basket. What happened?

PS: None of the fish were eaten, lost, or thrown back.