Naughty was reading a 161-page story book, and accidentally closed it. He remembered that the sum of the two pages he had just read was 81. If you read 30 pages a day for the rest, how many days will it take to finish reading?
淘气正在读一本161页的故事书，不小心合上了，他记得刚读完的两页页码之和是81．剩下没读的如果每天读30页，还要几天读完？
<gadget id="calculator">161 - 41</gadget>
<output>120</output>

<gadget id="calculator">120 / 30</gadget>
<output>4</output>

<result>4</result>