According to the information provided, if the credit card debt is 8,000 yuan, the minimum monthly repayment amount depends on the policy of the credit card issuing bank. Generally speaking, the minimum repayment amount is usually a certain proportion of the arrears, such as 5% of the total amount or 10%. At the same time, the interest of credit card is calculated according to the annual interest rate, and the specific interest rate also depends on the policies and agreements of the issuing bank.

The following is a detailed explanation of the answer:

1. Minimum repayment amount: The minimum repayment amount of a credit card is usually a certain proportion of the arrears. Assuming that the minimum repayment amount is 5% of the arrears, then the minimum repayment amount of the arrears of 8,000 yuan is 8,000 yuan multiplied by 5%, which is equal to 400 yuan.

2. Interest calculation: the interest on credit card arrears is calculated at the annual interest rate, but monthly. The specific interest rate depends on the policies and agreements of the credit card issuing bank, and is generally between 18%-25%. Taking the annual interest rate of 20% as an example, the monthly interest is 20% of the arrears divided by 12, that is, 8000 yuan multiplied by 20% divided by 12, which is about 133.33 yuan.

3. Summary: If the credit card debt is 8,000 yuan, assuming that the minimum repayment amount is 5% of the debt, the minimum monthly repayment amount is 400 yuan, and the monthly interest is about 133.33 yuan at the annual interest rate of 20%.

This is an answer based on the information provided. If you need to know more about the specific minimum repayment amount and interest calculation method, please consult the corresponding credit card issuer.

Extended data:

When using a credit card, if only the minimum repayment amount is paid, it means that the remaining arrears will continue to accumulate interest, resulting in higher interest expenses. It is suggested to pay off all debts as much as possible to avoid paying extra interest.

If you can't repay on time, it is recommended to contact the credit card issuing bank as soon as possible to find out the possible repayment arrangement and interest calculation method. Banks may offer plans such as installment payment or interest rate adjustment to help users repay their loans better.

When using a credit card, it is an important way to maintain a good credit record and avoid high interest expenses by reasonably controlling consumption and repayment amount and repaying on time.