The school allocates student dormitories. If there are 12 people in each room, there is just one room missing; if there are 15 people in each room, there is exactly one room vacant. How many students are there in total?
学校分配学生住宿，如果每个房间住12人，恰好缺一个房间；如果每个房间住15人，又恰好空出了一个房间．问住宿的学生共有多少人？
<gadget id="calculator">12 + 15</gadget>
<output>27</output>

<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<gadget id="calculator">27 / 3</gadget>
<output>9</output>

<gadget id="calculator">9 + 1</gadget>
<output>10</output>

<gadget id="calculator">12 * 10</gadget>
<output>120</output>

<result>120</result>