There is a cake, father and mother each ate (1/5) of this cake, and Dongdong ate the rest. How much of this cake did Dongdong eat?
有一个蛋糕，爸爸和妈妈各吃了这个蛋糕的(1/5)，剩下的全部被东东吃完了．东东吃了这个蛋糕的几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) + (1/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>