Which number should replace the question mark?

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

Two guards were guarding the camp.Guard-1 was looking towards the south to make sure no threat is coming from the road.Guard-2 was looking at the north to make sure no threat is coming from the top. Suddenly Guard-1 ask the Guard-2 why he is smiling?How Guard-1 knows that Guard-2 is smiling?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

I have a head like a cat and feet like a cat, but I am not a cat. What am I?

A clock loses 10 minutes each hour. If the clock is set correctly at noon, what time is it when it reads 3 PM?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

How many sides does a circle have?

I have nine bottles of wine and one of the nine bottles is poisoned.
I need to find the poisoned bottle with two facts
(1) Poison is deadly, only a sip will cost death
(2) I have two mice to do so.

How should I do it?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?