Solution ratio: ((x)/42)=((0.9)/18), (3/4): x=(5/16): (1/4).
解比例：((x)/42)=((0.9)/18)，(3/4)：x=(5/16)：(1/4)．
<gadget id="calculator">3 / 16</gadget>
<output>3/16 = around 0.1875</output>

<gadget id="calculator">5 / 16</gadget>
<output>5/16 = around 0.3125</output>

<gadget id="calculator">(3/16) / (5/16)</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>