There are 50 students in Class 51, 15 students participated in the Chinese interest group, and 20 students participated in the mathematics interest group. There are 8 people who participated in both the language and mathematics groups, and how many people did not participate in these two interest groups.
五1班有学生50人，参加语文兴趣小组的有15人，参加数学兴趣小组的有20人．语、数小组都参加的有8人，这两个兴趣小组都没有参加的有多少人．
<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<gadget id="calculator">15 + 12</gadget>
<output>27</output>

<gadget id="calculator">50 - 27</gadget>
<output>23</output>

<result>23</result>