There are upper and lower bookshelves in the bookshelf, and the number of books on the upper floor is 4 more than three times the number of books on the lower floor. If 5 books are taken from the lower shelf and placed on the upper floor, the number of books on the upper floor is 5 times the number of books on the lower floor. How many books are there?
书架中有上、下两层书，上层的本数比下层的本数的3倍多4本，如果从下层的书架中取出5本放在上层，则上层的本数是下层本数的5倍，书架中共有多少本书？
<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<gadget id="calculator">25 + 4 + 5</gadget>
<output>34</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">34 / 2</gadget>
<output>17</output>

<gadget id="calculator">3 * 17</gadget>
<output>51</output>

<gadget id="calculator">17 + 51 + 4</gadget>
<output>72</output>

<result>72</result>