For a barrel of oil, 1/3 of the barrel of oil is used for the first time, and 30 kilograms are used for the second time, and half of the barrel of oil is left. How many kilograms of this barrel of oil are there?
一桶油，第一次用去这桶油的(1/3)，第二次用去30千克，还剩下这桶油的一半，这桶油有多少千克？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

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

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

<result>180</result>