The books on shelf A belong to shelf B (5/8). If 21 books are taken from shelf B and put into shelf A, then the number of books on the two shelves is equal. How many books are there on shelf B?
甲书架的书是乙书架的(5/8)，若从乙书架取21本书放入甲书架，则两个书架的本数相等，乙书架原来有多少本书？
<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">1 - (5/8)</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">2 / (3/8)</gadget>
<output>16/3 = around 5.333333</output>

<gadget id="calculator">21 * (16/3)</gadget>
<output>112</output>

<result>112</result>