If a batch of books is 20 books per package, 18 packages should be bundled; if each package is 30 books, how many packages should be bundled?
一批书如果每包20本，要捆18包，如果每包30本，要捆几包？
<gadget id="calculator">20 * 18</gadget>
<output>360</output>

<gadget id="calculator">360 / 30</gadget>
<output>12</output>

<result>12</result>