Naomi invested $3,425 in an account that pays 3% simple annual interest. what was the total balance in the account after 15 years?

Each year, your $3,425 which earn 3% simple interest earns $102.75. Multiplying this value by 15 gives $1541.25. Then, adding the latest value we have with the initial invest will finally give us $4966.25. Thus, after 15 years Naomi will have $4966.25.