17. Mingming's mother found an interesting phenomenon while shopping. Every time she paid, the amount of money in her wallet was exactly 5 times the amount she paid. After settling the bill twice, she still had 320 yuan left in her wallet. How much money did she have in her wallet before she started shopping?
【Analysis】Each time a payment is made, the amount in the wallet is 5 times the amount paid, so after the payment, the amount in the wallet is 4 times the amount paid. Therefore, the second payment was $320 \div 4=80$ yuan, and before the payment, there was 400 yuan. The first payment was $400 \div 4=100$ yuan, and before the payment, there was 500 yuan.