The sum of the numerator and denominator of a simplest proper fraction is 12, what is the possible number of this fraction
一个最简真分数的分子与分母的和是12，这个分数的可能是多少
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

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