A book has 120 pages, after reading (2/5), how many pages are left.
一本书120页，看了(2/5)，还剩多少页．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">120 * (3/5)</gadget>
<output>72</output>

<result>72</result>