There are less than 50 students in a class. In an exam, (1/7) students get "excellent", (1/3) students get "good", and (1/2) students get "pass". So how many people "failed"?
某班学生人数不到50人，在一次考试中，有(1/7)的学生得"优"，(1/3)的学生得"良"，(1/2)的学生"及格"．那么有多少人"不及格"？
<gadget id="calculator">7 * 3 * 2</gadget>
<output>42</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">42 * (1/7)</gadget>
<output>6</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">42 * (1/3)</gadget>
<output>14</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">42 * (1/2)</gadget>
<output>21</output>

<gadget id="calculator">42 - 6 - 14 - 21</gadget>
<output>1</output>

<result>1</result>