A book has 200 pages, 45% of which have been read, and how many pages are left unread.
一本书有200页，看了45%，还剩下多少页没有看．
<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (9/20)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">200 * (11/20)</gadget>
<output>110</output>

<result>110</result>