Hongxing Coal Mine mined 351,000 tons of coal in September, 57,000 tons less than twice the amount in August. How many tons of coal did Hongxing Coal Mine mine in August?
红星煤矿九月份采煤35.1万吨，比八月份的2倍少5.7万吨．红星煤矿八月份采煤多少万吨？
<gadget id="calculator">35.1 + 5.7</gadget>
<output>40.8</output>

<gadget id="calculator">40.8 / 2</gadget>
<output>20.4</output>

<result>20.4</result>