Put 7 red balls and 5 green balls in a box, draw a ball randomly from the box, what is the probability of drawing a red ball?
把7个红球，5个绿球放在一个盒子里，从盒里任意摸出一个球，摸出红色球的可能性是多少．
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<result>7/12 = around 0.583333</result>