Xiao Liang ate (2/7) and Xiao Lan ate (3/7) a piece of birthday cake, how much did they eat altogether? What fraction is left?
一块生日蛋糕，小亮吃了(2/7)，小兰吃了(3/7)，他们一共吃了几分之几？还剩几分之几？
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1 - (5/7)</gadget>
<output>2/7 = around 0.285714</output>

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