piece of cake, the elder brother ate (3/9), the older sister ate (4/9), and the rest was given to the younger sister. How much of the cake did the younger sister eat?
一块蛋糕，哥哥吃了(3/9)，姐姐吃了(4/9)，剩下的给妹妹，妹妹吃了这块蛋糕的几分之几？
<gadget id="calculator">3 / 9</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">1 - (1/3) - (4/9)</gadget>
<output>2/9 = around 0.222222</output>

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