The school holds a table tennis competition, and there are 7 students signing up. If every two students play a game, how many games will be played in total?
学校进行乒乓球比赛，有7个同学报名，若每两名同学进行一场比赛，一共要进行多少场比赛．
<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<result>21</result>