Final answer:
The incorrect method for credit card companies to figure interest is 'adjusted yearly balance'. Credit cards typically use average daily balance, adjusted balance, or previous balance methods.
Step-by-step explanation:
The method not used by credit card companies to figure interest is b. adjusted yearly balance. Credit card companies use various methods to calculate the interest charges on your outstanding balance. The most common methods include the average daily balance, which takes into account the balance on each day of the billing cycle, and the adjusted balance, which takes the balance at the beginning of the billing cycle and subtracts any payments made during that cycle. Lastly, the previous balance method uses the balance at the end of the previous billing cycle to determine the interest.