It costs 36 yuan to buy an iron pencil case and a double-layer plastic pencil case, and 9 yuan for an iron pencil case. How many times is a double-layer plastic case an iron pencil case?
买一个铁铅笔盒和一个双层塑料铅笔盒共用去36元，一个铁铅笔盒9元，一个双层塑料盒是一个铁铅笔盒的多少倍？
<gadget id="calculator">36 - 9</gadget>
<output>27</output>

<gadget id="calculator">27 / 9</gadget>
<output>3</output>

<result>3</result>