The library is full of seats. After one class, the readers leave (1/8), and 21 people come in. At this time, there are not enough seats, so there are 12 people crowded together to sit on a stool. How many seats are there in the school library? seat?
图书馆内座无虚席，一节课后，看书的走了(1/8)，又进来21人，这时座位不够了，只好有12人两人挤在一起座一个凳子，学校图书馆共有多少个座位？
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">21 - 6</gadget>
<output>15</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">15 / (1/8)</gadget>
<output>120</output>

<result>120</result>