(3/5): x = (4/5): (4/7).
(3/5)：x=(4/5)：(4/7)．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(3/5) * (4/7)</gadget>
<output>12/35 = around 0.342857</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(12/35) / (4/5)</gadget>
<output>3/7 = around 0.428571</output>

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