The school holds a storytelling session. In the audience, there is one high-grade student among two people; one middle-grade student among four people; and one low-grade student among seven people. There are 6 teachers. How many people are in the audience?
学校举行一次故事会．听众里每两人中有一个高年级学生；四人中有一个中年级学生；七人中有一个低年级学生．还有6位老师．问听众有多少人？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

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

<gadget id="calculator">1 - (1/2) - (1/4) - (1/7)</gadget>
<output>3/28 = around 0.107143</output>

<gadget id="calculator">6 / (3/28)</gadget>
<output>56</output>

<result>56</result>