The mother squirrel picked 24 pine nuts per day on sunny days and 16 on rainy days. He picked a total of 168 pine nuts for several days, with an average of 21 per day. How many sunny days were there in these days?
松鼠妈妈采松子，晴天每天可采24个，雨天每天可采16个，他一连几天一共采了168个松子，平均每天采21个，这几天当中一共有多少天晴天．
<gadget id="calculator">168 - 128</gadget>
<output>40</output>

<gadget id="calculator">24 - 16</gadget>
<output>8</output>

<gadget id="calculator">40 / 8</gadget>
<output>5</output>

<result>5</result>