Subtract a number from the numerator of the fraction (55/64), and add this number to the denominator at the same time, the fraction obtained after simplification is (4/13), what is the subtracted number.
分数(55/64)的分子减去一个数，分母同时加上这个数后所得的分数化简后为(4/13)，减去的这个数是多少．
<gadget id="calculator">4 / 13</gadget>
<output>4/13 = around 0.307692</output>

<gadget id="calculator">(4/13) * 64</gadget>
<output>256/13 = around 19.692308</output>

<gadget id="calculator">55 - (256/13)</gadget>
<output>459/13 = around 35.307692</output>

<gadget id="calculator">1 + (4/13)</gadget>
<output>17/13 = around 1.307692</output>

<gadget id="calculator">(459/13) / (17/13)</gadget>
<output>27</output>

<result>27</result>