The package tickets for Zhongshan Park used to be 20 yuan each, with a 15% discount during the June 1st period. How much can you save by buying a set of such packages during June 1st?
中山公园的游园套票原来每套20元，六一期间八五折优惠．六一期间购买一套这样的套票能省多少元．
<gadget id="calculator">85 / 100</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">1 - (17/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">20 * (3/20)</gadget>
<output>3</output>

<result>3</result>