There are white balls in a box and 18 red balls in total. If one ball is drawn from the box, the probability of drawing a white ball is (2/3), so how many red balls are there in total?
一个盒子里有白球，红球共有18个，从盒里摸出1个球，摸出白球的可能性是(2/3)，那么红球一共有多少个．
<gadget id="calculator">18 - 12</gadget>
<output>6</output>

<result>6</result>