One day at noon, the reading room of the students in Huji Center Primary School was full of seats. Half an hour later, the students who were reading books left (1/8), and 21 students came in at the same time. Sit on chairs together. How many seats are there in the reading room?
一天中午胡集中心小学学生阅览室里座无虚席，半小时后看书的人学生走了(1/8)，同时又进来21个学生，这时座位不够了，只好有18个学生每两人挤在一起坐椅子．阅览室里共设了多少个座位？
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">21 - 9</gadget>
<output>12</output>

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

<gadget id="calculator">12 / (1/8)</gadget>
<output>96</output>

<result>96</result>