3. (10 points) Meteorological records of a certain region indicate that during a certain period, it rained all day for 1 day; it rained during the day and was clear at night, or was clear during the day and rained at night for 9 days; there were 6 clear nights and 7 clear days. Therefore, the total number of days during this period is $\qquad$ days, of which the number of days that were clear all day is $\qquad$ days.
【Analysis】A day has two parts: daytime and nighttime. It rains in 9 parts, and it does not rain in $(6+7)$, which is 13 parts. Therefore, the number of days that are not completely rainy is: $(9+13) \div 2=11$ (days); the total number of days is: $11+1=12$ (days). Among the 11 days, the number of days with some rain is 9, so the number of days with no rain at all is: $11-9=2$ (days).

【Solution】Solution: Clear during the day or night: $6+7=13$ (parts);
The number of days that are not completely rainy is: $(9+13) \div 2=11$ (days);
The total number of days is: $11+1=12$ (days);
Completely clear days: $12-9=2$ (days).
Answer: This period has 12 days, among which there are 2 completely clear days.
Therefore, the answers are: 12, 2.