Hi there! I can help you.
Rate: To find the rate, let’s divide interest earned by the principal. When you do, you get 0.15. Multiply by 100 to get 15 and divide by 3 to get 5. The simple interest rate is 5%.
New balance: All you have to do is add the principal and he new balance. When you do, you get 517.5. The new balance is $517.50.