A pile of cement is used up (2/5) and there are still 9 tons left. How many tons is this pile of cement?
一堆水泥用去它的(2/5)还剩9吨，这堆水泥原有多少吨．
<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">9 / (3/5)</gadget>
<output>15</output>

<result>15</result>