There are two layers of books on the bookshelf, with a total of 240 books. If 24 books are taken from the upper layer and placed on the lower layer, the number of books on the two layers will be the same. How many books are there on the upper layer of the bookshelf?
书架上有两层书，共240本，如果上层取24本放到下层去，两层书的本数就相同，书架上层有多少本书．
<gadget id="calculator">24 * 2</gadget>
<output>48</output>

<gadget id="calculator">240 + 48</gadget>
<output>288</output>

<gadget id="calculator">288 / 2</gadget>
<output>144</output>

<result>144</result>