The general formula of simple interest formula is: I = PRT where I = simple interest, P = principal amount, R = interest rate, T = time (in years). Given that the initial investment is $70, the interest rate is 3% (or 0.03 as a decimal) and the time is 12 years, you can form the following:
Nothing is 100% certain no matter how sure it seems. This is especially true with statistics. There's always going to be some amount of error. The goal is to minimize the error as much as possible in the best cost-effective manner.
If a question has four possible answers, and you are strictly guessing regarding which of them is correct, then the chances of your choosing the correct one from the four is 1 in 4, or 0.25.
