(8/9)-((2/9)+(4/7)).
(8/9)-((2/9)+(4/7))．
<gadget id="calculator">8 / 9</gadget>
<output>8/9 = around 0.888889</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(2/9) + (4/7)</gadget>
<output>50/63 = around 0.793651</output>

<gadget id="calculator">(8/9) - (50/63)</gadget>
<output>2/21 = around 0.095238</output>

<result>2/21 = around 0.095238</result>