China won a total of 100 medals in the 2008 London Olympics, including 51 gold medals and 21 silver medals. How many bronze medals are there?
2008年伦敦奥运会中国共获得奖牌总数是100枚，其中金牌51枚，银牌21枚，铜牌是多少枚？
<gadget id="calculator">100 - 51 - 21</gadget>
<output>28</output>

<result>28</result>