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

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 of five consecutive positive integers is $n$. If the next two integers are also included,the average of all these integers will

Out of $9$ persons,$8$ persons spent $Rs. 30$ each for their meals. The ninth one spent $Rs. 20$ more than the average expenditure of all the nine. The total money spent by all of them was (in $Rs.$)

The average weight of a group of $20$ boys was calculated to be $89.4 \text{ kg}$ and it was later discovered that one weight was misread as $78 \text{ kg}$ instead of the correct one of $87 \text{ kg}$. The correct average weight is in $\text{kg}$.

The average age of a man and his two twin sons,born on the same day,is $30 \, \text{years}$. The ratio of the ages of the father and one son is $5:2$. What is the father's age in $\text{years}$?