There are 30 coins of 1 yuan and 5 jiao, totaling 25 yuan, how many 5 jiao coins are there?
现有30枚1元和5角的硬币，总共25元，那么5角的硬币有多少枚．
<gadget id="calculator">30 * 1</gadget>
<output>30</output>

<gadget id="calculator">30 - 25</gadget>
<output>5</output>

<gadget id="calculator">1 - 0.5</gadget>
<output>0.5</output>

<gadget id="calculator">5 / 0.5</gadget>
<output>10</output>

<result>10</result>