class of students went rowing, and they calculated that if one more boat is added, each boat will take exactly 6 people; if one boat is reduced, each boat will take exactly 9 people. How many people are there in this class?
有一班同学去划船，他们算了一下，如果增加一条船，每条船正好坐6人；如果减少一条船，每条船正好坐9人．这班有多少人．
<gadget id="calculator">6 + 9</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 * 6</gadget>
<output>30</output>

<gadget id="calculator">30 + 6</gadget>
<output>36</output>

<result>36</result>