There is a barrel of oil, 25% is poured out for the first time, 15 kg is poured out for the second time, and the sum of the previous two times is poured out for the third time. At this time, 12.5% of the oil in the barrel is left. How many kilograms of oil?
有一桶油，第一次倒出25%，第二次倒出15千克，第三次倒出的是前两次的和，此时还剩下这桶油的12.5%，这桶没原有油多少千克？
<gadget id="calculator">15 + 15</gadget>
<output>30</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">12.5 / 100</gadget>
<output>0.125</output>

<gadget id="calculator">1 - (1/4) - (1/4) - 0.125</gadget>
<output>0.375</output>

<gadget id="calculator">30 / 0.375</gadget>
<output>80</output>

<result>80</result>