The store came in with 36 bicycles, sold (1/4) of the total in the first week, and (1/9) of the total in the second week. How many bicycles were sold in two weeks?
商店进来36辆自行车，第一周卖出总数的(1/4)，第二周卖出总数的(1/9)，两周共卖出自行车多少辆？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/4) + (1/9)</gadget>
<output>13/36 = around 0.361111</output>

<gadget id="calculator">36 * (13/36)</gadget>
<output>13</output>

<result>13</result>