There are 7 red balls and 2 white balls in a box, what is the probability of touching the white ball
盒子里有7个红球和2个白球，摸到白球可能性多少
<gadget id="calculator">7 + 2</gadget>
<output>9</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<result>2/9 = around 0.222222</result>