A batch of books is distributed to the first and second grades at a ratio of 3:5. It is known that the first grade has 5 books less than the second grade. How many books are there in this batch?
一批图书按3：5分给一、二年级，已知一年级比二年级少分了5本，这批图书共几本？
<gadget id="calculator">3 + 5</gadget>
<output>8</output>

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

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<result>20</result>