Filmore has invested $10,000 in an account to help pay for his grandson’s education. He expects the account to return 4.5% annually. Use the rule of 72 to estimate how long it will take the $10,000 to double in value.

Use a calculator basically

Where’s the problems ? ?

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.