There are 120 books in the sixth grade, which is 20% less than that in the fifth grade. How many books are there in the fifth grade?
六年级有图书120本，比五年级少20%，五年级有多少本图书？
<gadget id="calculator">20 / 100</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">120 / (4/5)</gadget>
<output>150</output>

<result>150</result>