In class 1 of the third year, 18 students participated in the Chinese interest group, 20 students participated in the mathematics interest group, and 5 students participated in both Chinese and mathematics. How many people are there in these two interest groups?
三年1班参加语文兴趣小组的学生有18人，参加数学兴趣小组的有20人，语文、数学都参加的有5人．这两个兴趣小组共有多少人．
<gadget id="calculator">18 - 5</gadget>
<output>13</output>

<gadget id="calculator">20 + 13</gadget>
<output>33</output>

<result>33</result>