A fraction after division is (3/7), if the sum of numerator and denominator before division is 80, then what is the fraction before division.
一个分数约分后是(3/7)，若约分前分子与分母的和是80，那么约分前分数为多少．
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<result>3/7 = around 0.428571</result>