A barrel of oil, if half of it is used up, the remaining oil in the barrel weighs 100 kilograms in total, and if (2/3) of the barrel of oil is used up, the remaining oil in the barrel weighs 70 kilograms in total. How many kilograms?
一桶油，如果用去一半后，剩下的油连桶共重100千克，如果用去这桶油的(2/3)后，剩下的油连桶共重70千克，原来这桶油有多少千克？
<gadget id="calculator">100 - 70</gadget>
<output>30</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(2/3) - (1/2)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">30 / (1/6)</gadget>
<output>180</output>

<result>180</result>