The Cultural Palace Cinema is playing a new movie. The movie tickets cost 20 yuan each. Ding Ding and his parents go to buy tickets with a discount card. Each ticket is 15% off. How much does it cost to buy three tickets?
文化宫电影院正在播放一部新电影，电影票每张票价20元，丁丁和父母拿着优惠卡去买票，每张票打八五折，买三张票共花多少元．
<gadget id="calculator">85 / 100</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">20 * (17/20) * 3</gadget>
<output>51</output>

<result>51</result>