It's really strange to say that there is a chicken mixed in the duck team, counting up to 9th, and counting down to 18th, please do the math, how many ducklings there are in total.
说稀奇真稀奇，鸭子队伍里混只鸡，顺着数它第9，倒着数它18，请你算一算，小鸭子一共有多少只．
<gadget id="calculator">18 - 1 - 1</gadget>
<output>16</output>

<gadget id="calculator">9 + 16</gadget>
<output>25</output>

<result>25</result>