There are 5 yellow balls and 8 red balls, what is the probability of drawing a yellow ball?
有5个黄球和8个红球，摸到黄球的可能性是多少．
<gadget id="calculator">5 + 8</gadget>
<output>13</output>

<gadget id="calculator">5 / 13</gadget>
<output>5/13 = around 0.384615</output>

<result>5/13 = around 0.384615</result>