Xiao Ling reads a 290-page novel, 20 pages a day for the first 4 days. After reading 30 pages a day, how many days can I finish it?
肖玲看一本290页的小说，前4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 * 4</gadget>
<output>80</output>

<gadget id="calculator">290 - 80</gadget>
<output>210</output>

<gadget id="calculator">210 / 30</gadget>
<output>7</output>

<result>7</result>