Sonia received a statement on her Certificate of Deposit showing that her investment had returned $4,320 over its life. If the Certificate of Deposit pays a simple interest rate of 4.8% and her initial investment was $12,000, how long had the money been invested?

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.