There is a barrel of oil, 1/5 of the barrel of oil is taken out for the first time, 12 kilograms of the barrel is taken out for the second time, and 50% of the barrel of oil is taken out twice, how many kilograms of this barrel of oil are there?
有一桶油，第一次取出这桶油的1/5，第二次取出12千克，两次共取出这桶油的50%，这桶油共有多少千克？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">12 / (3/10)</gadget>
<output>40</output>

<result>40</result>