In a bookshelf, there are 52 more books on the upper level than on the lower level. After taking 6 books from the upper level to the lower level, the books on the lower level are the upper level (2/3). How many books are there on the upper level of this bookshelf? (Solution of column equation)
一个书架，上层的书比下层多52本，从上层拿6本到下层后，下层的书是上层的(2/3)，这个书架上层原有多少书？(列方程解)
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">6 * (2/3)</gadget>
<output>4</output>

<gadget id="calculator">52 - 4 - 6</gadget>
<output>42</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">42 / (1/3)</gadget>
<output>126</output>

<result>126</result>