(7/9)-((2/3)-(2/5)).
(7/9)-((2/3)-(2/5))．
<gadget id="calculator">7 / 9</gadget>
<output>7/9 = around 0.777778</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/3) - (2/5)</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">(7/9) - (4/15)</gadget>
<output>23/45 = around 0.511111</output>

<result>23/45 = around 0.511111</result>