Can you replace the question mark with the correct number?

Forwards I am heavy, backward I am not. What am I?

What is so fragile that saying its name breaks it?

You find yourself in a strange place guarded by two guards.One of the guard always say truth while other always lies.You don't know the identity of the two.You can ask only one question to go out from there. What should you ask?

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 = ?

Count the number of squares in the picture below.

If eleven plus two equals one, what does nine plus five equal?

Can you count the number of blocks in the picture below?

Count the squares in the matchstick puzzle below?

Can you make a six-letter word using the letters N, A and B ?