A's number is 50, B's number is 20, and B's number is less than A's number.
甲数是50，乙数是20，乙数比甲数少多少．
<gadget id="calculator">50 - 20</gadget>
<output>30</output>

<gadget id="calculator">30 / 50</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>