A pile of coal has already been transported (2/5). If another 50 tons are transported, the remaining coal will be 30 tons less than the one already transported. How many tons is this pile of coal?
运一堆煤，已经运了(2/5)，如果再运50吨，则剩下的煤比已运的少30吨．这堆煤原有多少吨？
<gadget id="calculator">50 - 30</gadget>
<output>20</output>

<gadget id="calculator">50 + 20</gadget>
<output>70</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 2</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">70 / (1/5)</gadget>
<output>350</output>

<result>350</result>