The ratio of A and B is 5:4, A's number is 20, how much more A's number than B's number.
甲、乙两数的比是5：4，甲数是20，甲数比乙数多多少．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20 * (4/5)</gadget>
<output>16</output>

<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<gadget id="calculator">4 / 16</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>