For the non-zero natural numbers a, b, c, specify the new operation "☆": ☆(a, b, c)=((ab/c)/(a+b*c)), then ☆(1, 2 , 3)=how much.
对不为零的自然数a，b，c，规定新运算"☆"：☆(a，b，c)=((a-b/c)/(a+b*c))，则☆(1，2，3)=多少．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">1 + 6</gadget>
<output>7</output>

<gadget id="calculator">(1/3) / 7</gadget>
<output>1/21 = around 0.047619</output>

<result>1/21 = around 0.047619</result>