please show formula approach

21. You ran a little short on your spring break vacation, so you put $1,000 on your credit card. You can afford only the minimum payment of $20 per month. The interest rate on the credit card is 1.5 percent per month. How long will you need to pay off the $1,000? 22. Suppose you borrow $2,000 at 5%, and you are going to make annual payments of $734.42. How long before you pay off the loan