A pile of muck is transported, the small cart transports away this pile of soil (2/5), the large cart transports more of this pile of soil than the small cart (1/7), how much is left that has not been transported away?
运一堆渣土，小车运走这堆土的(2/5)，大车比小车多运这堆土的(1/7)，还剩下多少没有运走？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/7) + (2/5)</gadget>
<output>19/35 = around 0.542857</output>

<gadget id="calculator">1 - (2/5) - (19/35)</gadget>
<output>2/35 = around 0.057143</output>

<result>2/35 = around 0.057143</result>