The numerator of a fraction is enlarged by 3 times, and the denominator is 2 (1/7) after being reduced by 3 times. What is the original fraction?
一个分数的分子扩大3倍，分母缩小了3倍后是2(1/7)，原来的分数是多少．
<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<gadget id="calculator">5 / 21</gadget>
<output>5/21 = around 0.238095</output>

<result>5/21 = around 0.238095</result>