Read an 810-page storybook, read 30 pages a day for the first 3 days, and read 80 pages a day for the rest, how many days will it take to finish reading?
读一本810页故事书，前3天每天读30页，其余每天读80页，还要几天读完？
<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<gadget id="calculator">810 - 90</gadget>
<output>720</output>

<gadget id="calculator">720 / 80</gadget>
<output>9</output>

<result>9</result>