(1/3): (1/20) = x: (5/9).
(1/3)：(1/20)=x：(5/9)．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">(1/3) * (5/9)</gadget>
<output>5/27 = around 0.185185</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(5/27) / (1/20)</gadget>
<output>100/27 = around 3.703704</output>

<result>100/27 = around 3.703704</result>