Let x = the amount of money Ruby had at first.
5x = the amount of money Ruby had before spending $80.
5x - 80 = the amount of money Ruby had after spending $80.
3/7(5x - 80) = the amount of money Sally had after Ruby spent $80.
3/7(5x - 80) = 3/7(5x) - 3/7(80)
3/7(5x) = 3/7(80) + 3/7(5x - 80)
3/7(5x) = 3/7(80) + Sally's amount of money
3/7(5x) = 3/7(80) + 3/7(5x - 80)
3/7(5x) = 3/7(80) + 3/7(5x) - 3/7(80)
3/7(5x) = 3/7(5x)
5x = 80
x = 16
Ruby had $16 at first.
Ruby had 5 times as much money as Sally. Ruby spent $80 and Sally had 3/7 as much as Ruby in the end. How much did Ruby have at first?
Show your work.
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