A barrel of oil weighs (17/18) kilograms. After half of the oil is used, the barrels still weigh (1/2) kilograms. How much does an empty barrel weigh?
一桶油连桶重(17/18)千克，用了油的一半后，连桶还重(1/2)千克，问空桶重多少千克？
<gadget id="calculator">17 / 18</gadget>
<output>17/18 = around 0.944444</output>

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

<gadget id="calculator">(17/18) - (1/2)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">(4/9) * 2</gadget>
<output>8/9 = around 0.888889</output>

<gadget id="calculator">(17/18) - (8/9)</gadget>
<output>1/18 = around 0.055556</output>

<result>1/18 = around 0.055556</result>