Add 4 to the numerator of a simplest fraction, and after the denominator is reduced to the original (1/4), the fraction value is equal to 1 (2/7). What is the simplest fraction?
给一个最简分数的分子加上4，分母缩小到原来的(1/4)后，分数值等于1(2/7)，这个最简分数是多少．
<gadget id="calculator">9 - 4</gadget>
<output>5</output>

<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<gadget id="calculator">5 / 28</gadget>
<output>5/28 = around 0.178571</output>

<result>5/28 = around 0.178571</result>