Keyboard words are not in alphabetical order, Why?

You are given with the following sum. Each of the letters can be decoded as a digit. If we tell you that D = 5, then can you solve it entirely?

DONALD
+GERALD
=ROBERT

Can you solve the maths in the below-given picture equation?

How many Watermelons are there in the below picture?

Why Aeroplane windows are round?

I am eight letters long - "12345678"
My 1234 is an atmospheric condition.
My 34567 supports a plant.
My 4567 is too appropriate.
My 45 is a friendly thank-you.
My 678 is a man's name.

What word am I?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

There were two grandmothers and their two granddaughters.
There were two husbands and their two wives.
There were two fathers and their two daughters.
There were two mothers and their two sons.
There were two maidens and their two mothers.
There were two sisters and their two brothers.
Yet there are only six, who are buried here,
All are born legitimate and relationships clear.
How can this happen?

What part of the chicken has the most feathers?

Solve the below puzzle by replacing the question mark with the correct number.

3 6 12

4 8 16

5 10 ?