Mom bought some lychees, my brother ate some of them (2/7), and my brother ate as much as my brother. What fraction of these lychees are left?
妈妈买回来一些荔枝，哥哥吃了它的(2/7)，弟弟吃的和哥哥一样多．还剩下这些荔枝的几分之几？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(2/7) + (2/7)</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 - (4/7)</gadget>
<output>3/7 = around 0.428571</output>

<result>3/7 = around 0.428571</result>