Susan had a sum of money. She spent 1/5 of it in September, 1/4 of it in October, and $120 in November. After spending these amounts of money, she still had $540 left. How much money did she have at first? Let's answer step by step:
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Let X be the amount Susan had originally. Susan spent 1 / 5 * X in September, 1 / 4 * X in October, and $120 in November. Susan has X - 1 / 5 * X - 1 / 4 * X - $120 = $540 left. Combining like terms, we get 11 / 20 * X - $120 = $540. Adding $120 to both sides, we get 11 / 20 * X = $660. Dividing both sides by 11 / 20 we get X = $1200. The answer: 1200.
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