(Competition question) The third grade students participated in the broadcasting exercise competition. They lined up in 6 rows with the same number of people in each row. Zhang Jun was in the fourth row. The ninth person from the front and the twelfth person from the back. How many people participated in the competition?
(竞赛题)三年级同学参加广播操比赛，他们排成6行，每行人数相同，张军排在第四行，从前面数是第九人，从后面数是第十二人，三年级参加比赛的有多少人？
<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<gadget id="calculator">9 + 11</gadget>
<output>20</output>

<gadget id="calculator">6 * 20</gadget>
<output>120</output>

<result>120</result>