There is a batch of cement in the warehouse. After being shipped out (2/5), 120 tons are brought in again. At this time, the number of tons of cement in the warehouse is equivalent to the original (3/4). How many tons of cement were there in the warehouse?
仓库里有一批水泥，运出(2/5)后，又运进120吨，这时仓库里水泥的吨数相当于原来的(3/4)．仓库里原来有水泥多少吨．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<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">(3/4) - (3/5)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">120 / (3/20)</gadget>
<output>800</output>

<result>800</result>