A book has 400 pages in total, I read (3/5), how many pages are left.
一本书共400页，看了(3/5)，还剩多少页没看．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">400 * (3/5)</gadget>
<output>240</output>

<gadget id="calculator">400 - 240</gadget>
<output>160</output>

<result>160</result>