Xiaojie plans to finish his homework in 3 hours. He completed (2/5) of all homework in the first hour and (2/7) of all homework in the second hour. Then Xiaojie should complete a few percent of all homework in the third hour. How much?
小杰计划3个小时做完作业，第一小时完成了所有作业的(2/5)，第二小时完成了所有作业的(2/7)，那么小杰第三小时应完成所有作业的几分之几？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">(2/5) + (2/7)</gadget>
<output>24/35 = around 0.685714</output>

<gadget id="calculator">1 - (24/35)</gadget>
<output>11/35 = around 0.314286</output>

<result>11/35 = around 0.314286</result>