(4/9): (5/6) = how much: 15．
(4/9)：(5/6)=多少：15．
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">15 / (5/6)</gadget>
<output>18</output>

<gadget id="calculator">(4/9) * 18</gadget>
<output>8</output>

<result>8</result>