The number A is (4/5) of the number B, then how much less is the number A than the number B
甲数是乙数的(4/5)，则甲数比乙数少多少
<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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