The supermarket conducts a ball-touching activity. There are yellow, red and green balls in the box. The red balls account for 1/15 of the yellow balls, and the green balls are 1/9. There are 30 yellow balls. , how many green balls are there?
超市进行摸球有奖活动，盒子里装有黄、红、绿三种颜色的球，红球占黄球的(1/15)，是绿球的(1/9)，黄球有30个，绿球有多少个？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/15) / (1/9)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">30 * (3/5)</gadget>
<output>18</output>

<result>18</result>