A barrel of oil, after 18 kilograms are used, there is still (2/5). How many kilograms is this barrel of oil?
一桶油，用去18千克后，还剩下(2/5)．这桶油多少千克？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">18 / (3/5)</gadget>
<output>30</output>

<result>30</result>