After a pile of coal is transported away (4/7), there are still 6 tons left. How many tons is this pile of coal? (Write the equality relationship first, and then use the equation to solve it)
一堆煤运走(4/7)后还剩6吨，这堆煤原有几吨？(先写相等关系，再用方程解答)
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 - (4/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">6 / (3/7)</gadget>
<output>14</output>

<result>14</result>