batch of books has sold 15 packs less than 37.5% of this batch of books. At this time, there are still 70% of this batch of books that have not been sold. How many packs of this batch of books are there?
一批图书，已经卖出的比这批书的37.5%少15包，这时还剩下这批书的70%没卖出，这批图书共有多少包？
<gadget id="calculator">37.5 / 100</gadget>
<output>0.375</output>

<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">0.375 - (3/10)</gadget>
<output>0.075</output>

<gadget id="calculator">15 / 0.075</gadget>
<output>200</output>

<result>200</result>