x-(1/9)=(7/18)-(3/7).
x-(1/9)=(7/18)-(3/7)．
<gadget id="calculator">7 / 18</gadget>
<output>7/18 = around 0.388889</output>

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

<gadget id="calculator">(7/18) - (3/7)</gadget>
<output>-5/126 = around -0.039683</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(-5/126) + (1/9)</gadget>
<output>1/14 = around 0.071429</output>

<result>1/14 = around 0.071429</result>