One wire is (4/5) meters long and the other is (1/7) meters shorter than it. How long is the other wire in meters?
一根铁丝长(4/5)米，另一根比它短(1/7)米，另一根长多少米．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">(4/5) - (1/7)</gadget>
<output>23/35 = around 0.657143</output>

<result>23/35 = around 0.657143</result>