certain class holds a chess game. There are 12 people participating in the chess game, 7 people participating in the Go game, and 3 people participating in both the chess game and the Go game. How many people participated in the chess game?
某班举行棋类比赛，参加象棋比赛的有12人，参加围棋比赛的有7人，既参加象棋比赛又参加围棋比赛的有3人，参加棋类比赛的共有多少人．
<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">12 + 4</gadget>
<output>16</output>

<result>16</result>