There are 18 white balls and 18 red balls in a box. They are identical except for their color. If a ball is randomly drawn from the box, the probability of getting 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18个，它们除颜色外完全相同，从盒子中任意摸出一个球，摸到白球的可能性为(2/3)，那么红球一共有多少个．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">18 * (1/3)</gadget>
<output>6</output>

<result>6</result>