There are 71 tortoises and cranes in the same pool, with a total of 228 feet. How many turtles are there?
龟鹤同池，共有71只，脚数共有228只．龟有多少只．
<gadget id="calculator">71 * 4</gadget>
<output>284</output>

<gadget id="calculator">284 - 228</gadget>
<output>56</output>

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

<gadget id="calculator">56 / 2</gadget>
<output>28</output>

<gadget id="calculator">71 - 28</gadget>
<output>43</output>

<result>43</result>