A certain convoy transports a pile of coal. On the first day, 1/6 of this pile of coal is transported away, and 30 tons more are transported on the second day than on the first day. At this time, the ratio of the coal that has been transported to the tonnage of the remaining coal is 7: 5. How many tons is this pile of coal?
某车队运一堆煤，第一天运走这堆煤的(1/6)，第二天比第一天多运30吨，这时已运走的煤与余下煤吨数比是7：5，这堆煤共有多少吨？
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(7/12) - (1/6) - (1/6)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">30 / (1/4)</gadget>
<output>120</output>

<result>120</result>