How many times can you subtract the number 5 from 25?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

There's one "sport" in which neither the spectators nor the participants know the score or the leader until the contest ends.

What is it?

You are mixing a mixture of cement and Sand with five gallons of water. You have a garden hose giving you all the water you need. The problem is that you only have a four-gallon bucket and a seven-gallon bucket and neither has graduation marks. Find a method to measure five gallons.

I can write cow in 13 letters.

Can You?

I organized a small get together at my home.
In the party , i have a barrel with some whiskey in it.

Suddenly Guest 1 say 'I bet this barrel of whiskey is more than half full'.
'No, it's less than half full' Guest 2 replied.

I don't have any measuring instrument and without removing whiskey from it , how can i determine which of the guest is right ?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

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?

This is a classy optical illusion puzzle. What more you can find except bricks in the image below?