The denominator of a fraction is the largest prime number within 10, and the numerator is both a prime number and an even number. What is the fraction?
一个分数的分母是10以内最大的质数，分子既是质数，又是偶数，这个分数是多少．
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<result>2/7 = around 0.285714</result>