Subtract a number from the denominator of a simplest fraction (13/27), add the same number to the numerator, and the new fraction can be reduced to (3/5). What is the number?
一个最简分数(13/27)的分母减去一个数，分子加上同一个数，所得的新分数可以约简为(3/5)，这个数是多少．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) * 27</gadget>
<output>81/5 = around 16.2</output>

<gadget id="calculator">(81/5) - 13</gadget>
<output>16/5 = around 3.2</output>

<gadget id="calculator">1 + (3/5)</gadget>
<output>8/5 = around 1.6</output>

<gadget id="calculator">(16/5) / (8/5)</gadget>
<output>2</output>

<result>2</result>