The teacher bought 13 boxes of pens and distributed them to the students. The number of pens in each box was the same, and the number of pens everyone got was the same. The teacher bought 3 more boxes of pens, and after sending them the same number of pens, there were 2 left. Later, 10 students came, and after the teacher bought 4 more boxes of pens, all of them happened to be finished. May I ask: How many students did you have?
老师买了13盒钢笔分给同学们，每盒钢笔的支数都相同，每人拿到的钢笔数目也相同，分完后发现剩下了半盒，这时又来了8名同学，于是老师又买了3盒钢笔，给他们发了同样数目的钢笔后，还剩下2支，后来又来了10名同学，老师又买了4盒钢笔后，正好全部分完．请问：原来有多少名同学？
<gadget id="calculator">13 - 0.5</gadget>
<output>12.5</output>

<gadget id="calculator">2 / 8</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) + (1/5)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">3.5 / 8</gadget>
<output>0.4375</output>

<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">0.4375 - (2/5)</gadget>
<output>0.0375</output>

<gadget id="calculator">(9/20) / 0.0375</gadget>
<output>12</output>

<gadget id="calculator">4 * 12</gadget>
<output>48</output>

<gadget id="calculator">48 + 2</gadget>
<output>50</output>

<gadget id="calculator">50 / 10</gadget>
<output>5</output>

<gadget id="calculator">(9/20) / 0.0375 / 5</gadget>
<output>2.4</output>

<gadget id="calculator">12.5 * 2.4</gadget>
<output>30</output>

<result>30</result>