Xiaogang reads a 230-page storybook, 15 pages in the first 6 days, and 20 pages a day after that, how many days can he finish it?
小刚看一本230页的故事书，前6天看了15页，以后每天看20页，再用几天可以看完？
<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">230 - 90</gadget>
<output>140</output>

<gadget id="calculator">140 / 20</gadget>
<output>7</output>

<result>7</result>