The number A is 20, the number B is 15, (20-15)/20=5/20=25%, which means how much less the number B is than the number A
甲数是20，乙数是15，(20-15)/20=5/20=25%，表示乙数比甲数少多少
<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<gadget id="calculator">5 / 20</gadget>
<output>1/4 = around 0.25</output>

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