The difference between the numerator and the denominator of a fraction is 3. If 13 is added to both the numerator and the denominator, it can be reduced to (6/7). Find the original fraction.
一个分数的分子，分母相差3，如果分子、分母同时加上13后，可约简成(6/7)，求原分数．
<gadget id="calculator">6 / 7</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">(6/7) * 13</gadget>
<output>78/7 = around 11.142857</output>

<gadget id="calculator">(78/7) - 13</gadget>
<output>-13/7 = around -1.857143</output>

<gadget id="calculator">3 + (-13/7)</gadget>
<output>8/7 = around 1.142857</output>

<gadget id="calculator">1 - (6/7)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(8/7) / (1/7)</gadget>
<output>8</output>

<gadget id="calculator">8 - 3</gadget>
<output>5</output>

<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<result>5/8 = around 0.625</result>