On the beach by the sea, there are 12 turtles and cranes with 30 legs. How many cranes are there?
海边的沙滩上，海龟和仙鹤共有12只，有30条腿．仙鹤有多少只．
<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">30 - 24</gadget>
<output>6</output>

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

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<result>9</result>