The number of A is 18, and the number of B is 15, (18-15)/18=(1/6), which means how much less B is than A
甲数是18，乙数是15，(18-15)/18=(1/6)，表示乙比甲少多少
<gadget id="calculator">18 - 15</gadget>
<output>3</output>

<gadget id="calculator">3 / 18</gadget>
<output>1/6 = around 0.166667</output>

<result>1/6 = around 0.166667</result>