batch of goods was shipped, and 75% of the total was shipped in the first week. If another 180 tons were shipped, it would exceed the plan (1/5). How many tons is this shipment?
运送一批货物，第一周运了总数的75%，如果再运180吨，就超过计划的(1/5)．这批货物有多少吨？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(1/5) - (3/4)</gadget>
<output>-11/20 = around -0.55</output>

<gadget id="calculator">1 + (-11/20)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">180 / (9/20)</gadget>
<output>400</output>

<result>400</result>