If EELS + MARK + BEST + WARY = EASY

What does HELP + BARK + WARD + LEAD equal?

I came first on earth but second on the heaven.
I also came twice in a week but found just once in a year.
I stay away from months but you can find me in February.

What am I?

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

John was drowned by he was not wet. How?

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?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

Replace the question mark with the correct number.

2 + 2= 4
3 + 3= 18
4 + 4= 48
5 + 5= ?

What does this rebus riddle means ?

If,

A + B = C
D - C = A
E - B = C

Based on the above equations, find out the answer for:

D + F = ?