The school organizes interest group activities. There are 36 people participating in the calligraphy group, which is 9 people less than 2.5 times that of the art group. How many people participate in the art group?
学校开展兴趣小组活动，参加书法组的有36人，比美术组的2.5倍少9人，参加美术组的有多少人？
<gadget id="calculator">9 + 36</gadget>
<output>45</output>

<gadget id="calculator">45 / 2.5</gadget>
<output>18</output>

<result>18</result>