Solution ratio: ((x+3)/7)=((2x)/5).
解比例：((x+3)/7)=((2x)/5)．
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(2/5) - (1/7)</gadget>
<output>9/35 = around 0.257143</output>

<gadget id="calculator">(3/7) / (9/35)</gadget>
<output>5/3 = around 1.666667</output>

<result>5/3 = around 1.666667</result>