There are 7 red balloons, 4 yellow balloons, and 2 blue balloons, and the blue balloons account for ((())/(())) of the total.
红气球有7个，黄气球有4个，蓝气球有2个，蓝气球占总数的((())/(()))．
<gadget id="calculator">7 + 4 + 2</gadget>
<output>13</output>

<gadget id="calculator">2 / 13</gadget>
<output>2/13 = around 0.153846</output>

<result>2/13 = around 0.153846</result>