The average of the first $25$ numbers is $10$ and the average of the next $25$ numbers is $12$. The average of all $50$ numbers is:

The average age of $5$ members is $21 \text{ years}$. If the age of the youngest member is $5 \text{ years}$,find out the average age of the family at the birth of the youngest member (in $\text{years}$).

The average marks in English subject of a class of $24$ students is $56$. If the marks of three students were misread as $44, 45$ and $61$ instead of the actual marks $48, 59$ and $67$ respectively,then what would be the correct average?

The average age of a group of $18$ persons is $32$ $years$ and $6$ $months$. If two persons of age $65$ $years$ each and one person of age $50$ $years$ leave the group,the average age of the remaining persons in the group will be (in $years$)

Find the average of all prime numbers between $60$ and $90$.

The average age of mother,father,and son was $42$ years at the time of the son's marriage. After one year,an infant was born in the family,and after $6$ years of marriage,the average age of the family is $36$ years. What was the age of the bride at the time of marriage in years?