The students in the Meteorological Team calculated that the average temperature for several days was 16 degrees. After the review, it was found that when calculating the temperature, the temperature of 21 degrees on a certain day was mistakenly calculated as 12 degrees. After recalculation, the average temperature of these days was 19 degrees. , the students of the meteorological team counted the temperature for a few days?
气象小组的同学统计了若干天的平均温度是16度，事后复查发现，计算温度时将某一天气温的21度误作12度计算了，经重新计算后，这几天的平均温度是19度，气象小组的同学统计了几天的温度？
<gadget id="calculator">21 - 12</gadget>
<output>9</output>

<gadget id="calculator">19 - 16</gadget>
<output>3</output>

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

<result>3</result>