There are a total of 20 hard pens with five cents and one yuan. Xiaojun counted them, and it was exactly 16 yuan. How many hard pens are there for one yuan?
现有五角和一元的硬笔共20个，小军数了数，刚好16元，一元的硬笔有多少枚？
<gadget id="calculator">20 * 1</gadget>
<output>20</output>

<gadget id="calculator">20 - 16</gadget>
<output>4</output>

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

<gadget id="calculator">4 / 0.5</gadget>
<output>8</output>

<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<result>12</result>