Ian had twenty roses. He gave six roses to his mother, nine roses to his grandmother, four roses to his sister, and he kept the rest. How many roses did Ian keep? Give me reasons, before answering the question

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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Ian gave a total of 6 + 9 + 4 = 19 roses. Therefore, Ian kept 20 - 19 = 1 rose. So the final answer is 1.