The ratio of teachers having a flip phone to teachers having a smartphone was 3: 4 if 15 teachers more teachers have a smart phone than a flip phone. how many teachers own a flip phone

At the beginning of year 1, carlos invests $600 at an annual compound interest rate of 4%. he makes no deposits to or withdrawals from the account. which explicit formula can be used to find the account's balance at the beginning of year 5? what is, the balance?