The harder way is to wokr out a formula.
Say you start with 1 dollar, and you get 6.5% interest per year.
so each year, you multiply what you have in the account by 1.065
so year 0 you have $1, year 1 you have $1*1.065, year 2 you have $1*1.065*1.065
Now we see that we can turn this into a pattern:

where n is the number of years.
Now you want 2 dollars at the end of the day, so you need to solve
Are you studying logarithms? Can you solve this for n?