A 20-meter rope, the first use of the full length (2/5), the second use of the first (3/4), how many meters left?
一根20米的绳子，第一次用了全长的(2/5)，第二次用去第一次的(3/4)，还剩下多少米？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 * (2/5)</gadget>
<output>8</output>

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

<gadget id="calculator">20 * (2/5) * (3/4)</gadget>
<output>6</output>

<gadget id="calculator">20 - 8 - 6</gadget>
<output>6</output>

<result>6</result>