The average of $25$ results is $20$. The average of the first $12$ results is $15$ and that of the last $12$ results is $18$. Then,the $13^{th}$ result is:

The average age of $20$ boys in the class is $15.6$ years. Five new boys join and the new average becomes $15.56$ years. What is the average age of the five new boys (in years)?

The average age of a cricket team reduces by $2$ when two senior players aged $32$ and $30$ are replaced by $2$ youngsters of equal age. What is the age of these youngsters?

After replacing an old member with a new member,it was found that the average age of five members of a club is the same as it was $3 \, \text{years}$ ago. What is the difference between the ages of the replaced member and the new member (in $\text{years}$)?

The average score of Rahul,Manish,and Suresh is $63$. Rahul's score is $15$ less than Ajay and $10$ more than Manish. If Ajay scored $30$ marks more than the average score of Rahul,Manish,and Suresh,what is the sum of Manish's and Suresh's scores?

In a family,the average age of a father and a mother is $35 \text{ years}$. The average age of the father,mother,and their only son is $27 \text{ years}$. What is the age of the son (in $\text{years}$)?