Megan is an actress. She was the lead actress in 80% of her work. In total, Megan participated in 100 plays. How many times Megan was not the lead actress? Let's answer step by step:

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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Megan was the lead actress in 100 * 80% = 80 plays. So Megan was not the lead actress in 100 - 80 = 20 plays. The answer: 20.