There are 18 people in the six-year class of Guangming Primary School participating in the art interest group, which is 20% more than the number of people participating in the sports interest group. How many people participate in the sports interest group?
光明小学六年一班参加美术兴趣小组的有18人，比参加体育兴趣小组的人数多20%，参加体育兴趣小组的有多少人？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">18 / (6/5)</gadget>
<output>15</output>

<result>15</result>