There are 26 people in the art interest group who are required to bring two kinds of painting tools to the class, but 2 people do not bring painting tools, among them, 13 people bring crayons, and 18 people bring watercolor pens. How many people are there with both?
美术兴趣小组有26人上课，要求带两种绘画工具，有2人没带绘画工具，其中带蜡笔的有13人，带水彩笔的有18人．两种都带的有多少人？
<gadget id="calculator">18 + 13</gadget>
<output>31</output>

<gadget id="calculator">26 - 2</gadget>
<output>24</output>

<gadget id="calculator">31 - 24</gadget>
<output>7</output>

<result>7</result>