There are 16 bills of 2 yuan and 5 yuan in total, with a total value of 59 yuan. How many pieces of 5 yuan are there?
2元和5元的钱共16张，共值59元，5元的有多少张．
<gadget id="calculator">16 * 5</gadget>
<output>80</output>

<gadget id="calculator">80 - 59</gadget>
<output>21</output>

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

<gadget id="calculator">21 / 3</gadget>
<output>7</output>

<gadget id="calculator">16 - 7</gadget>
<output>9</output>

<result>9</result>