There are 9 students in the art interest group of Xinxing Primary School, and there are as many students in the calligraphy interest group as in the art interest group. How many students are there in these two interest groups?
新星小学美术兴趣小组有学生9人，书法兴趣小组的人数和美术兴趣小组的人数同样多，这两个兴趣小组共有多少名学生？
<gadget id="calculator">9 + 9</gadget>
<output>18</output>

<result>18</result>