Put 10 yellow balls and 2 white balls in a cloth bag, touch one randomly at a time, and then put it back. How many more green balls need to be placed in order to make the probability of drawing a white ball (1/8).
把10个黄球和2个白球放在一个布袋里，每次任意摸一个，然后放回．要使摸出白球的可能性是(1/8)，需要再放入多少个绿球．
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">2 / (1/8)</gadget>
<output>16</output>

<gadget id="calculator">16 - 10 - 2</gadget>
<output>4</output>

<result>4</result>