Yimin Primary School planted 180 trees. Among them, (1/5) was planted in the fifth grade, and (1/4) was planted in the fourth grade. How many more trees were planted in the fourth grade than in the fifth grade?
益民小学植树180棵．其中(1/5)是五年级种的，(1/4)是四年级种的，四年级比五年级多植了多少棵树？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">180 * (1/20)</gadget>
<output>9</output>

<result>9</result>