A's number is 20, B's number is 50, and A's number is less than B's number.
甲数是20，乙数是50，甲数比乙数少多少．
<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>