There are 20 poplars in the campus, and the willows are poplars (9/10). How many willows are there?
校园里有杨树20棵，柳树是杨树的(9/10)，柳树有多少棵？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">20 * (9/10)</gadget>
<output>18</output>

<result>18</result>