A barrel of oil, the first use of this barrel of oil (1/6), the second use of 30 kilograms, and the remaining (1/2) of this barrel of oil, how many kilograms of this barrel of oil?
一桶油，第一次用去这桶油的(1/6)，第二次用去30千克，还剩下这桶油的(1/2)，这桶油有多少千克？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

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

<gadget id="calculator">1 - (1/6) - (1/2)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">30 / (1/3)</gadget>
<output>90</output>

<result>90</result>