The number of A is (4/15), less than the number of B (1/5), what is the number of B?
甲数是(4/15)，比乙数少(1/5)，乙数是多少．
<gadget id="calculator">4 / 15</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/15) / (4/5)</gadget>
<output>1/3 = around 0.333333</output>

<result>1/3 = around 0.333333</result>