Xiao Ming read an extra-curricular book. After reading it for a few days, the number of pages he had read was 1/8 of the remaining pages. Later, he read another 20 pages. At this time, the number of pages he had read was 1/8 of the remaining pages. Count (1/6), how many pages are there in this extracurricular reading?
小明看了一本课外读物，读了几天后，已读的页数是剩下页数的(1/8)，后来他又读了20页，这时已读的页数是剩下页数的(1/6)，这本课外读物共有多少页？
<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/7) - (1/9)</gadget>
<output>2/63 = around 0.031746</output>

<gadget id="calculator">20 / (2/63)</gadget>
<output>630</output>

<result>630</result>