The number A is 20 less than 80% of the number B, the number A is 40, what is the number B
甲数比乙数的80%少20，甲数是40，乙数是多少
<gadget id="calculator">40 + 20</gadget>
<output>60</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">60 / (4/5)</gadget>
<output>75</output>

<result>75</result>