There are 50 iron nails of two different sizes in the box, a total of 210 grams, each big nail weighs 5 grams, and the small nail weighs 3 grams, then how many big nails are more than small nails?
盒子里有两种大小不同的铁钉50个，一共有210克，大钉子每个重5克，小钉子重3克，则大钉子比小钉子多多少个．
<gadget id="calculator">5 * 50</gadget>
<output>250</output>

<gadget id="calculator">250 - 210</gadget>
<output>40</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">50 - 20 - 20</gadget>
<output>10</output>

<result>10</result>