There is a bucket of water. After pouring out (2/5), there is still 30L of water in the bucket. What is the original water in the bucket?
有一桶水，倒出(2/5)后，桶内还剩30L水，桶内原有水多少L．
<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">30 / (3/5)</gadget>
<output>50</output>

<result>50</result>