There are two layers of books on the bookshelf, the number of books on the second layer is (3/5) of the first layer. If 80 books are taken from the first floor and placed on the second floor, the number of books on the two shelves is equal. How many books are there on the first shelf?
书架上有两层书，第二层的本数是第一层的(3/5)．如果从第一层中取出80本放到第二层，则两层书架上的书本数相等．原来第一层书架上有多少本书？
<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(5/8) - (1/2)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">80 / (1/8)</gadget>
<output>640</output>

<gadget id="calculator">640 * (5/8)</gadget>
<output>400</output>

<result>400</result>