A piece of wood, (3/7) of it is used, and the rest is ((())/(())) of this piece of wood; if (3/4)m is left, how long is this piece of wood in m ．
一根木材，用去它的(3/7)，剩下的是这根木材的((())/(()))；如果剩下(3/4)m，这根木材长多少m．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

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

<gadget id="calculator">1 - (3/7)</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(3/4) / (4/7)</gadget>
<output>21/16 = around 1.3125</output>

<result>21/16 = around 1.3125</result>