There are a total of 25 yuan in Xiao Ming's piggy bank, 15 one-yuan coins, and the rest are five-cent coins. How many five-cent coins are there?
小明的储蓄罐里一共有25元，一元硬币有15枚，其余的都是五角硬币，五角硬币有多少枚．
<gadget id="calculator">1 * 15</gadget>
<output>15</output>

<gadget id="calculator">25 - 15</gadget>
<output>10</output>

<gadget id="calculator">10 / 0.5</gadget>
<output>20</output>

<result>20</result>