The three of them ate a cake, Xiao Nan ate (3/7), Xiao Xi ate (2/7), how much did Xiao Bai eat?
一个蛋糕三人分着吃完，小南吃了(3/7)，小西吃了(2/7)，小白吃了几分之几？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (3/7) - (2/7)</gadget>
<output>2/7 = around 0.285714</output>

<result>2/7 = around 0.285714</result>