Teacher Chen wants to bring a sum of money to Xinhua Bookstore to buy a set of books divided into two volumes. If you only buy the first volume, you can buy exactly 10 books; if you only buy the second volume, you can buy exactly 15 books. Buy, exactly how many sets you can buy.
陈老师要带一笔钱到新华书店去买一种分上下册为一套的书，如果只买上册，正好可以买10本；如果只买下册，正好可以买15本，如果上下册都买，正好可以买多少套．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / (1/6)</gadget>
<output>6</output>

<result>6</result>