The sum of the numerator and denominator of a fraction is 67. If 5 is added to the numerator and denominator, the ratio of the numerator to the denominator is 2:5. What is the original fraction?
一个分数的分子与分母之和是67，如果把分子与分母各加上5，则分子与分母的比是2：5，原分数是多少．
<gadget id="calculator">67 + 5 + 5</gadget>
<output>77</output>

<gadget id="calculator">2 + 5</gadget>
<output>7</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">77 * (2/7)</gadget>
<output>22</output>

<gadget id="calculator">22 - 5</gadget>
<output>17</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">77 * (5/7)</gadget>
<output>55</output>

<gadget id="calculator">55 - 5</gadget>
<output>50</output>

<gadget id="calculator">17 / 50</gadget>
<output>17/50 = around 0.34</output>

<result>17/50 = around 0.34</result>