On Saturday, three members of Ding Ding’s family went to the zoo. Tickets for children were 4.5 yuan each, and tickets for adults were 8.5 yuan each. He entered the zoo with his father and mother. How much does it cost to buy tickets?
星期六，丁丁一家3人去动物园，儿童票每张4.5元，成人票每张8.5元，他和爸爸、妈妈一起人园，买门票要多少元钱？
<gadget id="calculator">8.5 * 2</gadget>
<output>17</output>

<gadget id="calculator">17 + 4.5</gadget>
<output>21.5</output>

<result>21.5</result>