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 = ?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

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

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

What occurs twice in a week, once in a year but never in a day?

What are the next two letters in the following series and why?
W A T N T L I T F S _ _

*Hint: Check Puzzle Title

I look at you, you look at me I raise my right, you raise your left. What am I?

There are nine letters in the below-given diagram. You have to form a nine-letter word using these letters.

A Child was born in Lahore, Pakistan. Still, the child is not a Pakistani citizen. why?

A Car is crossing a bridge 2 miles long. The bridge can only hold 10000 lbs, which is the exact weight of the car. The Car makes it half way across the bridge and stops. A bird lands on the car. Does the bridge collapse? Explain.