A batch of cement was transported away on the first day (3/10), and on the second day (2/5). The second day transported 8 tons more than the first day. How many tons is this batch of cement?
一批水泥，第一天运走(3/10)，第二天运走(2/5)，第二天比第一天多运走8吨．这批水泥共有多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/5) - (3/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">8 / (1/10)</gadget>
<output>80</output>

<result>80</result>