Okay, this is a pretty old puzzle now with a few variations, and yes, you can easily find the answer with a quick Google search, but for those who might never have encountered it before, here's the original version that I spent some hours trying to solve as a kid (back before you could just look up the answer on the Internet). And yes, I did manage to finally solve it and get the correct answer
So if you don't already know the answer, try to avoid looking it up and see how you go. It's similar in nature to the more modern sudoku puzzles, but not just limited to numbers.
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For the following clues, the general outline is that each house is a different colour and has an inhabitant of a different nationality, and those inhabitants all drink different beverages, own different pets, and smoke different brands of American cigarettes (which is one thing some of the variations change).
1. There are five houses.
2. The Englishman lives in the red house.
3. The Spaniard owns the dog.
4. Coffee is drunk in the green house.
5. The Ukrainian drinks tea.
6. The green house is immediately to the right (your right) of the ivory house.
7. The Old Gold smoker owns snails.
8. Kools are smoked in the yellow house.
9. Milk is drunk in the middle house.
10. The Norwegian lives in the first house.
11. The man who smokes Chesterfields lives in the house next to the man with the fox.
12. Kools are smoked in the house next to the house where the horse is kept.
13. The Lucky Strike smoker drinks orange juice.
14. The Japanese smokes Parliaments.
15. The Norwegian lives next to the blue house.
Now, who drinks water? Who owns the zebra?
This was taken from Wikipedia. I copied it rather than posting a link though as they also give the answer and discuss how to solve it.