Arithmetic Mean Questions

For the past five months, a merchant has made sales of Rs. 6,435, Rs. 6,927, Rs. 6,855, Rs. 7,230 and Rs. 6,562. What amount of sales does he need in the sixth month to achieve an average sale of Rs. 6,500?

The average revenues of $13$ consecutive years of a company is $\text{Rs }82\text{ lakhs}$. If the average of the first $7$ years is $\text{Rs }77\text{ lakhs}$ and that of the last $7$ years is $\text{Rs }89\text{ lakhs}$, find the revenue for the $7^{\text{th}}$ year.