The teacher uses part of the money to buy a batch of books to support the disaster area. If you buy both "Science World" and "Fairy Tale", you can buy 60 sets each. If you only buy 30 sets of "Science World" and 10 sets of "Fairy Tale", Then the ratio of the amount of money used to the amount of remaining money is 3:7. If you use all the money to buy "Science World", how many sets can you buy?
老师拿一部分钱购买一批图书支援灾区，如果《科学世界》和《童话故事》两种书都买，可以各买60套，如果只买《科学世界》30套和《童话故事》10套，则所用的钱数与剩下的钱数的比是3：7，如果用全部的钱购买《科学世界》可以买多少套？
<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">60 - 20</gadget>
<output>40</output>

<gadget id="calculator">4 / 40</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>3/2 = around 1.5</output>

<gadget id="calculator">(3/2) * 60</gadget>
<output>90</output>

<gadget id="calculator">90 + 60</gadget>
<output>150</output>

<result>150</result>