3 tons of coal are removed from a pile of coal, and 4 tons are left. How much of the pile of coal is removed
一堆煤运走了3吨，还剩下4吨，运走的占这堆煤的多少
<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<result>3/7 = around 0.428571</result>