How can you make number one disappear by adding something to it?

A little girl goes to the store and buys one dozen eggs. As she is going home, all but three break. How many eggs are left unbroken?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

An exterior architect is asked by a builder to plant seven trees in a manner that there are exactly six rows of trees in a straight line and each row has three trees in particular.

How will he do it?

If Bihan is 10, Anirudha is 20, and Kim and Seal are both 5, but Rikold is 10, how much is Kenniger by the same trend?

What numbers should go on the bottom line?
3 6 9 15
8 2 10 12
11 8 19 27
19 10 29 39
? ? ? ?

What does Alexander the Great and Winnie the Pooh have in common?

Solve the counting riddle by identifying the number of triangles in the given picture.

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

which number am I?

Spot 5 differences in two Christmas tree below: