If your credit card debt is only 9 yuan, and the minimum repayment amount of your debit card is 100 yuan, in this case, you can repay it in the following ways:

1. Use the online banking function of the debit card to repay the credit card online, and choose to pay it off in full.

2. Use third-party payment platforms such as Alipay and WeChat to transfer the arrears to the credit card repayment account through this platform, and also choose to pay off in full.

3. Go to the bank counter to handle the repayment business and pay in cash.

It should be noted that although your credit card debt is only 9 yuan, if you don't pay off the debt before the repayment date, there will be overdue penalty interest and late payment fee. Therefore, it is very important to repay the credit card arrears in time and avoid unnecessary expenses.