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 of $5$ consecutive integers starting with $m$ is $n$. What is the average of $6$ consecutive integers starting with $(m + 2)$?

The average salary of the entire staff in an office is $Rs. 500$ per day. The average salary of officers is $Rs. 750$ and that of non-officers is $Rs. 250$. If the number of officers is $15$,then find the number of non-officers in the office?

The average weight of $3$ persons is $65 \, kg$. If a fourth person having a weight of $45 \, kg$ joins the group,what is the average weight of the group? (in $kg$)

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 $\text{years}$)?

In a coconut grove,$(x+2)$ trees yield $60$ nuts per year,$x$ trees yield $120$ nuts per year,and $(x-2)$ trees yield $180$ nuts per year. If the average yield per year per tree is $100$,find the value of $x$.