(3/9) of the whole class cleans the classroom, (1/9) cleans the playground, and the number of people who clean the playground is less than the number of people who clean the classroom. What is the total number of people?
全班同学人数的(3/9)打扫教室，(1/9)的同学打扫操场，打扫操场的人数比打扫教室的人数少总人数的多少
<gadget id="calculator">3 / 9</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">(1/3) - (1/9)</gadget>
<output>2/9 = around 0.222222</output>

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