There are 12 sea turtles and seagulls on the beach by the sea, with 30 legs. How many seagulls are there?
海边的沙滩上海龟和海鸥共有12只，有30条腿，海鸥有多少只？
<gadget id="calculator">12 * 4</gadget>
<output>48</output>

<gadget id="calculator">48 - 30</gadget>
<output>18</output>

<gadget id="calculator">4 - 2</gadget>
<output>2</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<result>9</result>