There are 12 willows, less than poplar (1/5). How many poplars are there?
柳树有12棵，比杨树少(1/5)．杨树有多少棵？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">12 / (4/5)</gadget>
<output>15</output>

<result>15</result>