The library bought 180 science and technology books, and the science and technology books were 20 times less than the story books. How many story books did the library buy? (column equation solution)
图书馆买来科技书180本，科技书比故事书的2倍少20本，图书馆买来故事书多少本？(列方程解答)
<gadget id="calculator">180 + 20</gadget>
<output>200</output>

<gadget id="calculator">200 / 2</gadget>
<output>100</output>

<result>100</result>