There is a barrel of oil. After pouring out (3/5), there are 30 liters left in the barrel. How many liters is there in this barrel?
有一桶油，倒出(3/5)后，桶里还剩30升，这桶油原来有多少升？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">30 / (2/5)</gadget>
<output>75</output>

<result>75</result>