The whole class participated in field camping activities and received several tent lotuses. If you get one less, you can use it for 9 people in each tent; if you get one more, you can use it for 6 people in each tent. Please answer: how many people in this class participated in the activity.
全班同学参加野外露营活动，领到帐莲若干个．如果少领一个，每个帐蓬9人用；如果多领一个，每个帐蓬6人用．请回答：该班有多少人参加活动．
<gadget id="calculator">9 + 6</gadget>
<output>15</output>

<gadget id="calculator">9 - 6</gadget>
<output>3</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<result>36</result>