Fill in the vacant numbers according to the law: (1/3), (2/5), (3/7), (4/9), (5/11), how much, (7/15).
按规律填出空缺的数：(1/3)，(2/5)，(3/7)，(4/9)，(5/11)，多少，(7/15)．
<gadget id="calculator">2 * 6</gadget>
<output>12</output>

<gadget id="calculator">12 + 1</gadget>
<output>13</output>

<gadget id="calculator">6 / 13</gadget>
<output>6/13 = around 0.461538</output>

<result>6/13 = around 0.461538</result>