The ratio of number A to number B is 4:5, how much less number A is than number B
甲数与乙数的比是4：5，甲数比乙数少多少
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>