When Datouzi buys a certain commodity, if he only pays 2 yuan bills, the number of bills will be 9 more than that of only paying 5 yuan bills. What is the price of this commodity?
大头儿子买某一种商品，如只付2元钞票的张数将比只付5元钞票的张数多9张，这种商品的价格是多少元．
<gadget id="calculator">2 * 9</gadget>
<output>18</output>

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

<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<gadget id="calculator">6 * 5</gadget>
<output>30</output>

<result>30</result>