For a fraction, the sum of the numerator and the denominator is 67. If 13 is added to the denominator, the fraction can be reduced to (1/4). What is the original fraction?
一个分数，分子和分母的和是67，如果分母加上13，这个分数可化简为(1/4)，原来这个分数是多少．
<gadget id="calculator">67 + 13</gadget>
<output>80</output>

<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">80 * (1/5)</gadget>
<output>16</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">80 * (4/5)</gadget>
<output>64</output>

<gadget id="calculator">64 - 13</gadget>
<output>51</output>

<gadget id="calculator">16 / 51</gadget>
<output>16/51 = around 0.313725</output>

<result>16/51 = around 0.313725</result>