There are 5 white balls, 4 red balls, and 3 black balls in a bag, what is the probability of drawing a black ball?
一个袋子里有5个白球，4个红球，3个黑球，摸出黑球的可能性是多少．
<gadget id="calculator">3 + 4 + 5</gadget>
<output>12</output>

<gadget id="calculator">3 / 12</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>