A story book has 300 pages, I have already read it (7/15), how many pages are left unread.
一本故事书300页，已经读了(7/15)，还剩多少页没有读．
<gadget id="calculator">7 / 15</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">1 - (7/15)</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">300 * (8/15)</gadget>
<output>160</output>

<result>160</result>