A rope is (3/2) meters long, (3/7) is used for the first time, and (3/7) meters is used for the second time. How many meters are left.
一根绳子长(3/2)米，第一次用去(3/7)，第二次又用去(3/7)米．还剩下多少米．
<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(3/2) * (3/7)</gadget>
<output>9/14 = around 0.642857</output>

<gadget id="calculator">(3/2) - (9/14) - (3/7)</gadget>
<output>3/7 = around 0.428571</output>

<result>3/7 = around 0.428571</result>