Element X is a radioactive isotope such that every 16 years, its mass decreases by half. Given that the initial mass of a sample of Element X is 430 grams, how long would it be until the mass of the sample reached 190 grams, to the nearest tenth of a year?

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.