A rope is used up (1/5), and there is (3/5) meter left, how many meters is this rope long?
一根绳子用去(1/5)，还剩(3/5)米，这根绳子长多少米．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(3/5) / (4/5)</gadget>
<output>3/4 = around 0.75</output>

<result>3/4 = around 0.75</result>