Two bookshelves, (1/4) of the books stored in the A bookshelf is equivalent to (2/5) of the B bookshelf, and the A bookshelf stores 120 more books than the B bookshelf. How many books are stored on the B bookshelf?
两个书架，甲书架存书的(1/4)相当于乙书架的(2/5)，甲书架比乙书架多存120本．乙书架存书多少本．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/5) / (1/4)</gadget>
<output>8/5 = around 1.6</output>

<gadget id="calculator">(8/5) - 1</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">120 / (3/5)</gadget>
<output>200</output>

<result>200</result>