A tractor plowed the whole field in 3 hours (7/9), according to this calculation, how much time will it take to plow the field?
一台拖拉机3小时耕了整块地的(7/9)，照这样计算，还需要多少时间才能耕完这块地？
<gadget id="calculator">7 / 9</gadget>
<output>7/9 = around 0.777778</output>

<gadget id="calculator">1 - (7/9)</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">(7/9) / 3</gadget>
<output>7/27 = around 0.259259</output>

<gadget id="calculator">(2/9) / (7/27)</gadget>
<output>6/7 = around 0.857143</output>

<result>6/7 = around 0.857143</result>