A storybook shipped from the bookstore sells 30% on the first day and 50% on the second day, which is 60 more copies than the first day. How many books of this kind did the bookstore ship in total?
书店运来一种故事书，第一天卖出30%，第二天卖出50%，比第一天多卖60本，书店运来的这种故事书一共有多少本？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">60 / (1/5)</gadget>
<output>300</output>

<result>300</result>