A fraction, the sum of the numerator and the denominator is 84, the fraction is reduced to (5/7), what is the original fraction.
一个分数，分子和分母的和是84，这个分数约分后是(5/7)，原分数是多少．
<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">84 * (7/12)</gadget>
<output>49</output>

<gadget id="calculator">(5/12) / 49</gadget>
<output>5/588 = around 0.008503</output>

<gadget id="calculator">84 * (5/588)</gadget>
<output>5/7 = around 0.714286</output>

<result>5/7 = around 0.714286</result>