human
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?
assistant
How much money did Susan spend in September, October, and November? ** Let X be the amount Susan had originally. Susan spent 1/5*X in September, 1/4*X in October, and $120 in November.
How much money did Susan have left after spending? ** Susan has X - 1/5*X - 1/4*X - $120 = $540 left.
How much money did Susan have left after spending? ** Combining like terms, we get 11/20*X - $120 = $540
How much money did Susan have left after spending? ** Adding $120 to both sides, we get 11/20*X = $660.
How much money did Susan have at first? ** Dividing both sides by 11/20 we get X = $1200.
#### 1200