There are fewer story books in school than science books (1/5), exactly 100 fewer, how many science books are there? (solution by equation)
学校的故事书比科技书少(1/5)，刚好少100本，科技书有多少本？(用方程解)
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">100 / (1/5)</gadget>
<output>500</output>

<result>500</result>