Adding the same natural number to the numerator and denominator of (1/13) at the same time, the fraction obtained is equal to (1/2), what is the natural number?
将(1/13)的分子分母同时加上一个相同的自然数，得到的分数与(1/2)相等，这个自然数是多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">13 / 1</gadget>
<output>13</output>

<gadget id="calculator">(1/2) * 13</gadget>
<output>13/2 = around 6.5</output>

<gadget id="calculator">(13/2) - 1</gadget>
<output>11/2 = around 5.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(11/2) / (1/2)</gadget>
<output>11</output>

<result>11</result>