$\displaystyle \text{A football match is played between Team 1 and Team 2.}$

$\displaystyle \text{The probability that team 1 wins is }p\text{, and that team 2 wins is }q.$

$\displaystyle \text{The probability that they draw is }1 - p - q$.

$\displaystyle \text{If they draw, they rematch with the same probabilities as before.}$

$\displaystyle \text{In the event of a second draw, there is a sudden-death shootout}$

$\displaystyle \text{with each team having a 50\% chance of winning.}$

$\displaystyle \text{In terms of }p\text{ and }q\text{, what is the probability that Team 1 wins?}$