Since the annual interest rate is 10%, it means whatever amount of money you put into that account, you will get 10% of it more every year.

So for three years, if you put $100 into it, you're getting 10% of $100, which is just $10, for the first year.

$100 + $10 = $110

Second year:

$110 + $11 = $121

Third year:

$121 + $12.10 = **$133.10** <--- This is what you will have in three years.