Xiao Ming reads a 240-page story book, reads 20 pages a day for the first 3 days, and then reads 30 pages a day, how many days can he finish it?
小明看一本240页的故事书，前3天每天看20页，以后每天看30页，再用几天可以看完？
<gadget id="calculator">20 * 3</gadget>
<output>60</output>

<gadget id="calculator">240 - 60</gadget>
<output>180</output>

<gadget id="calculator">180 / 30</gadget>
<output>6</output>

<result>6</result>