$A$ student bought $4$ books for $Rs. 120$ from one book shop and $6$ books for $Rs. 150$ from another. The average price (in rupees),he paid per book was

$A$ number,$x$,equals $80 \%$ of the average of $5, 7, 14$ and a number $y$. If the average of $x$ and $y$ is $26$,then the value of $y$ is:

$A$ man spends $Rs. 1800$ monthly on an average for the first four months and $Rs. 2000$ monthly for the next eight months and saves $Rs. 5600$ a year. His average monthly income is (in $Rs.$)

The mean weight of $150$ students in a class is $60 \, kg$. The mean weight of boys is $70 \, kg$ and that of girls is $55 \, kg$. What is the number of boys in the class?

The average of $41$ consecutive odd numbers is $49$. What is the largest number?

The average age of a family of $6$ members is $22 \text{ years}$. If the age of the youngest member is $7 \text{ years}$,then what was the average age of the family at the birth of the youngest member?