There are 8 football teams playing a football match. If every 2 teams play a game, how many games are there in total?
有8支足球队进行足球比赛，如果每两支球队进行一场比赛，共比多少场．
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

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

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

<result>28</result>