A barrel of oil is used up (1/3), and there is still 80kg left. How much is the barrel of oil originally?
一桶油用去(1/3)，还剩下80kg，这桶油原来有多少．
<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">80 / (2/3)</gadget>
<output>120</output>

<result>120</result>