Zhang Ying borrowed a story book, originally planned to read 20 pages a day, and finished it in 9 days. Actually read 10 more pages every day, how many days did you actually finish reading? (Solve with ratio)
张英借了一本故事书，原计划每天读20页，9天读完．实际每天多读10页，实际多少天读完？(用比例解)
<gadget id="calculator">20 * 9</gadget>
<output>180</output>

<gadget id="calculator">20 + 10</gadget>
<output>30</output>

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

<result>6</result>