There is a barrel of oil, take out (1/4) of it for the first time, take 5 kg less than the first time for the second time, and there are still 20 kg left. How many kilograms is this barrel of oil originally?
有一桶油，第一次取出它的(1/4)，第二次比第一次少取5千克，这时还剩20千克．这桶油原来有多少千克？
<gadget id="calculator">20 - 5</gadget>
<output>15</output>

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

<gadget id="calculator">1 - (1/4) - (1/4)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">15 / (1/2)</gadget>
<output>30</output>

<result>30</result>