A pile of coal is used up (2/5) and exactly 45 tons are left. How many tons does this pile of coal have?
一堆煤用去(2/5)正好剩45吨，这堆煤原有多少吨．
<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">45 / (3/5)</gadget>
<output>75</output>

<result>75</result>