Valentina invested $6500 in a savings accoint with a yearly interest rate of 4% for 7 years. How much simple interest did she earn?

The equations is A = P (1 + r) ^t, where P is the amount invested, r is the interest rate, and t is the time. So A, your total amount in the bank account including interest, is equal to 6500 (1.04) ^7, which is The answer is $8553.56 (that's what I rounded to). That is your total, so subtract 6500 from that number and you'll get the interest amount.