For a barrel of oil, pour out the full barrel (1/6) for the first time, 30 kg less than the second time. At this time, the ratio of the remaining oil to the oil poured out twice is 5:7. How many kilograms of crude oil?
一桶油，第一次倒出全桶的(1/6)，比第二次少倒出30千克，这时剩下的油与两次倒出的油的比是5：7，这桶油原有多少千克？
<gadget id="calculator">5 + 7</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>