When Xiao Ming calculates (4/7)*(□+(2/3)), it becomes (4/7)*□+(2/3), how much is the difference between the calculation result and the correct answer.
小明在计算(4/7)*(□+(2/3))时，算成了(4/7)*□+(2/3)，计算结果与正确答案相差多少．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">8 / 21</gadget>
<output>8/21 = around 0.380952</output>

<gadget id="calculator">(2/3) - (8/21)</gadget>
<output>2/7 = around 0.285714</output>

<result>2/7 = around 0.285714</result>