If the ratio of A and B is 17:20, how much is A less than B?
甲、乙两数的比是17：20，则甲比乙少多少．
<gadget id="calculator">20 - 17</gadget>
<output>3</output>

<gadget id="calculator">3 / 20</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>