A barrel of oil, 12 kg is used for the first time, and (1/3) is used for the second time, leaving 8 kg. How many kilograms is this barrel of oil?
一桶油，第一次用去12千克，第二次用去(1/3)，还剩8千克．这桶油多少千克？
<gadget id="calculator">12 + 8</gadget>
<output>20</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">20 / (2/3)</gadget>
<output>30</output>

<result>30</result>