An urn contains 17 balls marked LOSE and 3 balls marked WIN. You and an opponent take turns selecting a single ball at random from the urn without replacement. The person who selects the third WIN ball wins the game. It does not matter who selected the first two WIN balls. Q) If you draw first, find the probability that your opponent wins the game on his second draw?
What I tried: Possibilities: {W,W,L,W} {L,W,W,W} {W,L,W,W} I summed up the probabilities and got an answer as 3/1140 = 1/380
The book's answer is 1/760
Where have I made the mistake?