A book has 180 pages, and 80 pages have been read, what fraction of the pages have been read compared to the pages that have not been read?
一本书180页，看了80页，看过的页数是没有看的页数的几分之几？
<gadget id="calculator">180 - 80</gadget>
<output>100</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>