Xiao Wang and 7 classmates participated in a class reunion. When they met, each of them would shake hands once. How many times should they shake hands in total?
小王和7名同学参加一次同学聚会，见面时，每两个都要握一次手，一共要握多少次．
<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<result>28</result>