Given the stream of consciousness rationale, provide a reasonable question and answer. Rationale: They have played 30 total games because 12 + 18 = 30. The proportion won by Archibald is .4 because 12 / 30 = .4. The percentage he has won in 40% because .4 x 100% = 40%.
 The question and answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Archibald and his brother are playing tennis against each other. Archibald has won 12 games and his brother has won 18. What percentage of games has Archibald won?
The answer is 40