A release-checked easy problem for training Conditional Probability, Discrete Random Variables.
Question
Three riflemen $X ,Y$ and $Z$ take turns shooting at a target. $X$ shoots first, $Y$ second, and $Z$ third, after which the cycle repeats with $X$ again and again, until one of the riflemen hits the target. Each shot hits the target with probability $50\%$, independent of other shots. Find the probability $X$ wins.
Practice focus
This Probability problem is tagged Conditional Probability, Discrete Random Variables. State the random variables and conditioning information explicitly, then check the result against boundary cases before opening hints or a solution.