Calculate the probability of two teams have been drawns If we know that team A had a $39\%$ chance of winning and team B $43\%$ chance of winning, how we can calculate the probability of the teams drawn?
My textbook mention the answer but I cannot understand the logic behind it. The answer is $18\%$. As working is not shown I guess that this is how the find $18\%$ probability of two teams withdrawn:
$$ (100\% - 39\%) - 43\% = 18\%$$
But I cannot understand the logic behind it. I appreciate if someone can explain it to me.

The total probability of all events in a given situation must equal 1 or 100%.  The probability that there is a win by EITHER team is the chance team A wins plus the chance team B wins.
This is 39% (A wins) + 43% (B wins) = 82% chance that there will be a win.
If you take the 82% away from probability of all events, 100%, 
100% - 82% = 18% that the teams draw (tie)
