There is a batch of goods in the warehouse. After being shipped out (3/5), 30 tons are brought in again. At this time, the goods in the warehouse are exactly the original (1/2). How many tons are there in the warehouse?
仓库里有一批货物，运出(3/5)后，又运进30吨，这时仓库里的货物正好是原来的(1/2)，仓库里原来有货物多少吨．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<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">(1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">30 / (1/10)</gadget>
<output>300</output>

<result>300</result>