$A$ batsman has a certain average in $11$ innings. In the $12^{\text{th}}$ innings,he scores $90$ runs and his average decreases by $5$. After the $12^{\text{th}}$ innings,what is his average?

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

The average age of students of a class is $15.8 \text{ years}$. The average age of boys in the class is $16.4 \text{ years}$ and that of the girls is $15.4 \text{ years}$. The ratio of the number of boys to the number of girls in the class is:

The average temperature from Monday to Wednesday is $37^{\circ}C$,while the average temperature from Tuesday to Thursday is $34^{\circ}C$. The temperature of Thursday is $\frac{4}{5}$ times that of Monday. Find the temperature of Thursday in $^{\circ}C$.

The average pocket money of $3$ friends $A, B,$ and $C$ is $Rs. 80$ per month. If $B$ spends double and $C$ spends triple of what $A$ spends during that month,and if the average of their unspent pocket money is $Rs. 60,$ then how much does $A$ spend (in $Rs.$)?

The average age of $8$ men is increased by $2$ years when $2$ of them,whose ages are $20$ years and $24$ years respectively,are replaced by $2$ women. What is the average age of these two women (in years)?