https://www.quora.com/A-chess-game-is-played-among-3-players-Rule-The-person-who-wins-a-match-will-then-compete-with-the-other-person-sitting-Suppose-Vishu-played-15-games-Magnus-plays-19-games-and-Topolov-plays-9-games-How-many-games-were-played-between-Vishu-and-Magnus

1st question:
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As prem rajan said, Sum of games played by all i.e, 15+19+9 = 43 is odd . so, answer to 1st question is “can’t be determined”.

This means something wrong in the question. Let’s find out where is that wrong and assume something to make it correct.

2nd question:
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Consider,
1) No.of games played by “Topolov” = 9

2) For every two games 1 game should be played by Topolov.

3) So, maximum no.of games will be 9*2 = 18

4)If the first game and last game played between Vishu and Magnus. Total no.of games = 19

5)where 19 is no.of games played by Magnus.  (Magnus carlson is the world champion who defeated anand. I think he should not loose a match.)

6) This means Magnus won all the matches and Vishu lost in every match.

7) so, No.of games played by Vishu is 10.

First game played between Vishu and Magnus from point 4.

so, every ODD numbered games is not played by Topolov.

answer: Topolov

if we see 1st question now, the answer is 10.