batch of cement was transported. On the first day, (2/7) of this batch of cement was transported, and the rest (3/4) was transported on the second day. After two days of transport, there were still 50 tons left. How many tons is this batch of cement originally?
运送一批水泥，第一天运了这批水泥的(2/7)，第二天运的是余下的(3/4)，运了两天后还剩下50吨没有运．这批水泥原有多少吨？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7)</gadget>
<output>5/7 = around 0.714286</output>

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

<gadget id="calculator">(5/7) * (3/4)</gadget>
<output>15/28 = around 0.535714</output>

<gadget id="calculator">1 - (2/7) - (15/28)</gadget>
<output>5/28 = around 0.178571</output>

<gadget id="calculator">50 / (5/28)</gadget>
<output>280</output>

<result>280</result>