The annual interest rate on the saving account of Xavier which is earned simple interest is 9%.
<h3>What is simple interest?</h3>
Simple interest is the amount charged on the principal amount with a fixed rate of interest for a time period. Simple interest calculated only on the principal amount.
The formula for the simple interest can be given as,

Here, (<em>I</em>) is the interest amount on the principal amount of (<em>P</em>) with the rate of (<em>r</em>) in the time period of (<em>t</em>).
Xavier opened a savings account with a deposit of $12,000. At the end of 3 years, the account balance was $12,324.
The principal amount is $12000 and the total amount is $12324. Thus, the interest earned by the Xavier is,

Total time period is 3 years and the account earned simple interest. Thus, put these values in the above formula as,

Hence, the annual interest rate on the saving account of Xavier which is earned simple interest is 9%.
Learn more about the simple interest here;
brainly.com/question/2294792