A two-tier bookshelf with 200 books in total. The lower level accounts for (3/5) of the total, and after buying a few books and putting them on the upper level, the upper level (6/23) is equal to the lower level (1/4). How many books did you buy?
一个两层书架，共有图书200本．下层占总数的(3/5)，又买了若干本放到上层后，上层本数的(6/23)就和下层本数的(1/4)相等．问又买了图书多少本？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

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

<gadget id="calculator">6 / 23</gadget>
<output>6/23 = around 0.26087</output>

<gadget id="calculator">(1/4) / (6/23)</gadget>
<output>23/24 = around 0.958333</output>

<gadget id="calculator">200 * (3/5) * (23/24)</gadget>
<output>115</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">200 * (2/5)</gadget>
<output>80</output>

<gadget id="calculator">115 - 80</gadget>
<output>35</output>

<result>35</result>