There are 36 people in the school interest group, and the ratio of male to female students is 7:2. Later, some boys participated, boys accounted for 80% of the total. How many people are there in the mathematics interest group now?
学校兴趣小组共有36人，其中男女生人数比是7：2．后又有一些男生参加，男生占总数的80%．现在数学兴趣小组有多少人？
<gadget id="calculator">7 + 2</gadget>
<output>9</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(2/9) / (1/5)</gadget>
<output>10/9 = around 1.111111</output>

<gadget id="calculator">36 * (10/9)</gadget>
<output>40</output>

<result>40</result>