There are 46 books on the upper shelf and 22 books on the lower shelf. If the number of books on the upper shelf is three times that of the lower shelf, how many books must be taken from the lower shelf and placed on the upper shelf.
书架上层有46本书，下层有22本书，要使上层的书是下层书的3倍，那么必须从下层拿多少本放到上层去．
<gadget id="calculator">46 + 22</gadget>
<output>68</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">68 / 4</gadget>
<output>17</output>

<gadget id="calculator">22 - 17</gadget>
<output>5</output>

<result>5</result>