The factory plans to deliver a batch of goods in three days. The number of boxes shipped on the first day (2/5), the ratio of the number of boxes shipped on the second day to the third day is 5:7, and the ratio of the second day to the third day is 5:7. Days less than 30 boxes shipped. How many boxes are there in total for this shipment?
工厂计划用三天运送一批货物，第一天运了这批货物的(2/5)，第二天与第三天运送的箱数之比是5：7，且第二天比第三天少运了30箱．这批货物共有多少箱？
<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">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">(7/12) - (5/12)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(3/5) * (1/6)</gadget>
<output>1/10 = around 0.1</output>

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

<result>300</result>