In the sixth grade of Yale School, (1/9) people participated in the Elite E class, and 4 students were added later. Now how many people in the sixth grade have participated in the elite E class?
雅乐学校六年级有(1/9)的人参加了精英E班，后来又增加了4个同学，实际参加精英E班的人数是没参加精英E班人数的(1/6)．现在六年级有多少人参加了精英E班．
<gadget id="calculator">1 + 6</gadget>
<output>7</output>

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

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/7) - (1/9)</gadget>
<output>2/63 = around 0.031746</output>

<gadget id="calculator">4 / (2/63)</gadget>
<output>126</output>

<gadget id="calculator">126 * (1/7)</gadget>
<output>18</output>

<result>18</result>