There are 10 red balls and 8 green balls in a box, what is the probability of touching the green ball?
一个盒子里有10个红球、8个绿球，摸到绿球的可能性是多少．
<gadget id="calculator">10 + 8</gadget>
<output>18</output>

<gadget id="calculator">8 / 18</gadget>
<output>4/9 = around 0.444444</output>

<result>4/9 = around 0.444444</result>