For a project, the planned (4/7) and (3/5) were completed in the first half of the month and the second half of the month respectively. How much of the full plan was overfulfilled this month.
一项工程，上半月和下半月分别完成了计划的(4/7)和(3/5)，这个月超额完成全计划的多少．
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) - 1</gadget>
<output>-2/5 = around -0.4</output>

<gadget id="calculator">(4/7) + (-2/5)</gadget>
<output>6/35 = around 0.171429</output>

<result>6/35 = around 0.171429</result>