There are 45 people in class 52, many of them participated in extracurricular groups, 12 people participated in the art group, 30 people participated in the Olympic array, 8 people did not participate in both groups, and some participated in both the art group and the Olympic array how many people?
五2班有45人，许多人参加课外小组，参加美术组的有12人，参加奥数组的有30人，两个组都没参加的有8个人，既参加美术组又参加奥数组的有多少人？
<gadget id="calculator">12 + 30</gadget>
<output>42</output>

<gadget id="calculator">45 - 8</gadget>
<output>37</output>

<gadget id="calculator">42 - 37</gadget>
<output>5</output>

<result>5</result>