How to solve

You have an investment account that started with $$3,00020$ years ago and which now has grown to $$12,000.$

a$.$ What annual rate of return have you earned $($you have made no additional contributions to the account$)?$

b$.$ If the investment account earns $15\%$ per year from now on$,$ what will the account's value be $20$ years from now?

a$.$ What annual rate of return have you earned $($you have made no additional contributions to the account$)?$

Your annual rate of return is $\%.($Round to two decimal places.$)$