A pile of coal, 30% of it was used up on the first day, and the rest is 200 tons more than what was used. How heavy is this pile of coal?
一堆煤，第一天用去了30%，剩下的比用去的多200吨，这堆煤有多重？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10) - (3/10)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">200 / (2/5)</gadget>
<output>500</output>

<result>500</result>