The number of books on the upper and lower shelves of a bookshelf is equal. Borrow 25% of the books from the upper layer, borrow (2/5) from the lower layer, and then take 15 books from the upper layer and put them on the lower layer. At this time, there are as many books on the two floors. How many books are there on the upper and lower shelves of the original bookshelf?
一个书架上、下两层放书的册数相等．上层书借走25%，下层借走(2/5)，然后从上层拿15册放在下层，这时两层的书同样多．原来书架的上、下层各放有多少册书？
<gadget id="calculator">15 + 15</gadget>
<output>30</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/5) - (1/4) - 1</gadget>
<output>-17/20 = around -0.85</output>

<gadget id="calculator">1 + (-17/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">30 / (3/20)</gadget>
<output>200</output>

<result>200</result>