In the sixth grade, 15 people participated in the mathematics interest group, which was more than the art interest group (1/4). How many people participate in the art interest group?
六年级参加数学兴趣小组的有15人，比参加美术兴趣小组的多(1/4)．参加美术兴趣小组的有多少？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + (1/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">15 / (5/4)</gadget>
<output>12</output>

<result>12</result>